It is interesting to note that this Engineer Cathedral is comprised of different structures, from the Roman Empire to the former Yugoslavia. Details pieced together from these design choices can better explain what sort of message was being conveyed.
Concept Art by Steve Messing
The shape of the memorial complex here at Grmeč appears to symbolize a newly breaking flower bud (Photo 5), which is itself may be a representation of newly emerging freedom and ‘birth’ brought about by the sacrifice of those who fought and died here. In addition, the interior of the bud is intended to represent the very heart of the Grmeč forest, where the hospital that operated here toiled to keep wounded soldiers alive. Meanwhile, the ‘flower bud’ shaped structure is juxtaposed by a circular pool — this positioning may be meant to symbolize a dualistic relationship, with the blossoming of the ‘flower bud’ up from the earth representing ‘life’ and ‘freedom’, the adjacent pool symbolizes all those soldiers who fell and succumb to the violence of war.
Rebirth on Planet 4
From the choice of this as the entrance to the Engineer Cathedral, I take the symbolism of meaning of a seed or rebirth as Alien Explorations Blog has drawn a parallel to.
In my podcast with Dane Hallett on Alien Day he has explained that Planet 4 is a very old seeded planet. Evidence to support this is in Prometheus and Alien: Covenant as the lake shown in the opening credits and during the flyover of the lander entering Planet 4.
As we know the Engineers were shown to be seeding a primitive Earth-like planet, and it has not been explicitly defined as Earth. Although that was part of the early concept script by Damon Lindelof, titled PARADISE.
Ozymandias and The song for the future
The left panel of Grmeč that is now vandalised used to bear the letters of the following poem
Translated from Serbian to English
Maybe another time will come
and other people, incomprehensible to us.
Maybe someone else would look at the eye
and we with them and those with us.
Maybe they’ll see our good
all our misery and all the misery of the world
and find, perhaps, that of our soul
He does not live any more than the echo of the echo.
Perhaps the value of human life
by measure, they value and value each other
and other thoughts, the feelings of others
their works will bear their strength.
Nevertheless, no matter what kind of people
they are, habits, tendencies, customs, era –
but we know: they will not be able
without mail passing by our grave.
– The song for the future by Vladimir Popovic[6,7]
Considering the poem David quotes in his mind during The Crossing and when looking over the ruins of the Engineer City with Walter, I think it is an interesting parallel with Ozymandias by Percy Bysshe Shelly.
“I met a traveller from an antique land, Who said—“Two vast and trunkless legs of stone stand in the desert… . Near them, on the sand, half sunk a shattered visage lies, whose frown, and wrinkled lip, and sneer of cold command, tell that its sculptor well those passions read which yet survive, stamped on these lifeless things, the hand that mocked them, and the heart that fed; and on the pedestal, these words appear: My name is Ozymandias, King of Kings; Look on my Works, ye Mighty, and despair! Nothing beside remains. Round the decay of that colossal wreck, boundless and bare the lone and level sands stretch far away.”
– Ozymandias BY PERCY BYSSHE SHELLEY
Concept Art by Wayne Haag
Early concept art contained William Blake’s The Body of Christ Borne to the Tomb which currently resides in the Tate museum. This fits with the early concept that Jesus was an emissary to the Engineers, and the human race crucified him. Bringing on their vengeance and started them on a path towards destroying Earth. The concept thought as being too on the nose was abandoned, but partial parallels such as this remain as suggestions in the piles of inspiration laid out by the director Ridley Scott and the design team.
A Game of Light and Darkness
Dušan Džamonja intention in building this monument was to create a structure that was a ‘game of light and darkness’. The bulges in the concrete fins are meant to be ‘positives’ while the recessed non-bulging areas are the hollows or ‘negatives’. These ‘negatives’ represent death and defeat, while the ‘positives’ represent life and victory. In an interview in which he describes the symbolism of his memorial sculpture at Kozara, Džamonja is quoted as saying:
“I built a tower divided along vertical lines in four sections with a rhythmic profile, negative and positive. These patterns change four times and create a unity, the tower. The symbology represents the antagonism between life and death and between life and heroism. To strengthen the sacred character of the symbol, I built the vertical structure with concrete and steel layers, so that the steel layers can reflect the sun, unveiling the light.”
The crowning jewel of the Engineer Cathedral is the base layer of Kozara. It is an interesting choice to place this on top of the dome. The symbolism representing the battle between life and death and between life and heroism is an interesting parallel to Sir Peter Weyland’s mission to LV223 to ask for more life, and the heroism displayed by many of the Prometheus crew sacrificing their lives in order to stop the Engineer destroying Earth. And of course, in opposition to that is David bringing death to Planet 4 and wiping out the Engineers. There’s no heroics there, but the cold calculated actions of a villain. His actions could be likened to Axis forces which bore down on Partisan rebels and peasant fighters at this spot during the Battle of Kozara in 1942, oppressing and subverting Partisan efforts, through the killing of soldiers and murdering of civilians.
The Roman Pantheon is the most preserved and influential building of ancient Rome. It is a Roman temple dedicated to all the gods of pagan Rome. As the brick stamps on the side of the building reveal it was built and dedicated between A.D 118 and 125.
The emperor Hadrian (A.D 117-138) built the Pantheon to replace Augustus’ friend and Commander Marcus Agrippa’s Pantheon of 27 B.C. which burnt to the ground in 80 A.D.
When approaching the front of the Pantheon one can see the inscription above still reads in Latin the original dedication by Marcus Agrippa. The inscription reads:
“Marcus Agrippa son of Lucius, having been consul three times made it”.
Despite all the marvelous building projects that the emperor Hadrian produced during his reign, he never inscribed his name to any, but one, the temple of his father Trajan. That is why the Roman Pantheon bears the inscription of Marcus Agrippa, and not the emperor Hadrian.
The pediment,(the triangle section above the inscription) is blank today, but there would have been sculpture that acted out the battle of the Titans. Great bronze doors guard the entrance to the cella and would have been covered in gold, but it has long since disappeared.
The original use of the Pantheon is somewhat unknown, except that is was classified as a temple. However, it is unknown as to how the people worshipped in the building, because the structure of the temple is so different from other traditional Roman temples such as in the Roman Forum.
The Pantheon exists today in such amazing form because the Byzantine emperor Phocas gave it to Pope Boniface the IV in A.D 608 and it was used as a church ever since. The Pantheon has been in use since the time it was built.
A link to the Titan Prometheus
Again there is much symbolism to this choice in architecture to represent the Engineer Civilisation, part of it is the obvious parallels to the building being a temple to all gods. As well as the missing depiction of The Battle of the Titans, representative of the Engineers, even the previous movie namesake of Prometheus was a Titan.
In relation to SPECIAL ORDER 899 it has been described as a place where the Engineers had carried out ceremonies and ritual sacrifice, there are many parallels to the Roman beliefs of the time. Blood sacrifices were believed to be the best way to communicate with the gods and sheep were often sacrificed to Jupiter(Jove gen. Iovis [ˈjɔwɪs]), is the god of the sky and thunder and king of the gods in Ancient Roman religion and mythology). If you look carefully at the tables in which David places the flare gun and Elizabeth Shaw’s body is laid, you can see a groove on the table which indicated channels for the blood to flow.
The Archaic Triad is a hypothetical theological structure (or system) consisting of the gods Jupiter, Mars and Quirinus. The three-function hypothesis of Indo-European society in prehistory, society was divided into three classes (priests, warriors and craftsmen) which had as their religious counterparts the divine figures of the sovereign god, the warrior god and the civil god. The sovereign embodied Jupiter which entailed omnipotence; thence, a domain extended over every aspect of nature and life. There have been many theories to the Engineer society containing many castes, and this Proto-Indo European structure could potentially fit.
It is believed that the colour relating to the sovereign is white. The Engineer dressed in white can be seen during the scene in which the Engineers are obliterated by David.
The three functions are interrelated with one another, overlapping to some extent; the sovereign function, although essentially religious in nature, is involved in many ways in areas pertaining to the other two. Therefore, Jupiter is the “magic player” in the founding of the Roman state and the fields of war, agricultural plenty, human fertility and wealth.
In Roman religion the usurpation of Saturn as king of the gods by Jupiter was not viewed by the Latins as violent or hostile; Saturn continued to be revered in his temple at the foot of the Capitol Hill
But if Saturn was related to Iuppiter Latiaris, the old Jupiter of the Latins. The ceremony held at the sanctuary of the Latiar Hill in Rome involved a human sacrifice, the blood of the victim was then cast upon the statue.
Beheading, a mode of executing capital punishment by which the head is severed from the body. The ancient Greeks and Romans regarded it as a most honourable form of death. 
All of these monuments are remnants of the past great civilisations, lost to time. Nothing stands forever, except perhaps these creations.
- Alien Explorations Blog Alien Covenant: Grmeč Monument to the Revolution referenced for the domed citadel entrance?
- Aliens Explorations Blog Alien Covenant: Wayne Haag’s shell like cathedral entrance
- Concept Art, Steve Messing on Instagram https://www.instagram.com/messingart/
- Stills from Alien: Covenant, Steve Messing on Instagram https://www.instagram.com/messingart/
- Grmeč image from jankempenaers.info
- Symbolism, Spomenik Database http://www.spomenikdatabase.org/grmec
- PARADISE by Damon Lindelof via AVP Galaxy https://www.avpgalaxy.net/files/scripts/script-paradise-lindelof.pdf
- Image of Grmeč engraving and Comment by Nelija Mihajlova on Spomenik Database http://www.spomenikdatabase.org/grmec
- The song for the future – Vladimir Popovic https://slikepartizana.wordpress.com/2017/06/21/pjesma-buducima-vladimir-popovic/
- Ozymandias by Percy Bysshe Shelley https://www.poetryfoundation.org/poets/percy-bysshe-shelley
- Grmeč , Spomenik Database Instagram https://www.instagram.com/p/BnoebKrHMTK/
- Concept art by Wayne Haag via Artstation https://www.artstation.com/artwork/mw2qe
- Kozara image from jankempenaers.info
- Symbolism, Spomenik Database http://www.spomenikdatabase.org/kozara
- Kozara, Spomenik Database on Instagram https://www.instagram.com/p/Bngsq2YASL6/
- Pantheon image from Imgur
- The Roman Pantheon https://www.rome.info/pantheon/
- Pantheon Image by aquanukes on Instagram https://www.instagram.com/aquanukes/
- Pantheon Image by nereyedergisi on Instagram https://www.instagram.com/nereyedergisi/
- Pliny Naturalis Historia X 16. A. Alföldi Zu den römischen Reiterscheiben in Germania 30 1952 p. 188 and n. 11 as cited by G. Dumézil La religion reomaine archaïque Paris 1974 2nd ed., It. tr. Milan 1977
- D. Briquel “Jupiter, Saturne et le Capitol” in Revue de l’histoire des religions 198 2. 1981 pp. 131–162; Varro V 42; Vergil Aeneis VIII 357-8; Dionysius Hal. I 34; Solinus I 12; Festus p. 322 L; Tertullian Apologeticum10; Macrobius I 7, 27 and I 10, 4 citing a certain Mallius. See also Macrobius I 7, 3: the annalistic tradition attributed its foundation to king Tullus Hostilius. Studies by E. Gjerstad in Mélanges Albert GrenierBruxelles 1962 pp. 757–762; Filippo Coarelli in La Parola del Passato 1741977 p. 215 f.
- A. Pasqualini “Note sull’ubicazione del Latiar” in MEFRA 111 1999 2 p[. 784–785 citing M. Malavolta “I ludi delle feriae Latinae a Roma” in A. Pasqualini (ed.) Alba Longa. Mito storia archeologia. Atti dell’incontro di studio, Roma-Albano laziale 27-29 gennaio 1994 Roma 1996 pp. 257–273; Eusebius De laude Constantini 13, 7 = MPG XX col. 1403–1404; J. Rives “Human sacrifice among Pagans and Christians” in Journal of Roman Studies LXXXV 1995 pp. 65–85; Iustinus Apologeticum II 12, 4–5; G. Pucci “Saturno: il lato oscuro” in Lares LVIII 1992 p. 5-7.
- Beheading, https://www.britannica.com/topic/beheading
- Decapitated Engineer by Matt Hatton on Instagram https://www.instagram.com/matthatt0n/