Kazan Square, 2, Saint Petersburg, 191186
The excitement began when proponents of alternative history noticed paintings by early 19th-century artists, for example,

Fyodor Alekseyev's "View of the Kazan Cathedral in Petersburg," from the Russian Museum collection

Andrey Martynov’s “View of the Kazan Cathedral” from the State Hermitage collection and

Swede Benjamin Patersen’s “Kazan Cathedral from the Nevsky Prospect side”
They attract attention not only because they recreate on canvas accurate views of the city in 1811 and depict the panorama of the Cathedral of the Kazan Icon of the Mother of God (Kazan Cathedral), built in 1811 according to the design of architect A. M. Voronikhin on the site of a small church, but also because they contain a certain mysterious obelisk.
According to reptiloid and Nosovsky supporters, it remained from an ancient city that existed on the site of present-day Saint Petersburg.
Indeed, the history of the obelisk is somewhat interesting. On Voronikhin’s 1810 drawing, not only two colonnades but also two obelisks on the northern and southern sides are depicted.

Source: Plan of Kazan Cathedral and the adjacent blocks and squares. According to the 1810 project. Illustration from the book "Russian Architecture." 1940
The history of the construction of the Kazan Cathedral is a major milestone in the history of St. Petersburg urban art. Built in a very short time, this majestic monument of Russian architecture amazes many generations with its magnificence and beauty. The Kazan Cathedral was built according to the design of architect Andrey Nikiforovich Voronikhin from 1801 to 1811. It was constructed on the site of Nevsky Prospect where a modest Church of the Nativity of the Virgin Mary stood. This church housed one of St. Petersburg’s main shrines — the miraculous icon of the Kazan Mother of God. The cathedral was built by order of Emperor Paul I specifically for this icon, as the cathedral church of Saint Petersburg.
The idea for this cathedral was conceived by Paul I long ago, when he was still heir to the throne. In 1781, Their Imperial Highnesses Pavel Petrovich and his wife Maria Feodorovna traveled under the names Count and Countess of the North (du Nor) from Petersburg on a long journey. The travelers were young and energetic; Pavel Petrovich was then 27 years old, and his wife Maria Feodorovna was 22. Behind them lay the still very small Russian capital by European standards, with mostly wooden buildings and poorly paved streets. At the beginning of Nevsky Prospect, near the Green Bridge over the Moika River, a remarkable brick building stood out above the others — the Stroganov Palace, which still survives today. By the Catherine Canal stood a stone church with wooden domes and a bell tower — the Church of the Nativity of the Blessed Virgin Mary. It was built by the order and at the expense of Anna Ioannovna and consecrated on June 13, 1737. It housed the shrine of the Romanov House and Russia — the Kazan Icon of the Mother of God.
They arrived in the Eternal City on February 12, 1782, five months after the start of their trip. St. Peter’s Basilica in the Vatican was already famous at that time. Its appearance inspired the tsesarevich with the idea of creating a church in Petersburg with the same colonnade, obelisk, and square in front of it. Already as emperor, he designated a place for it on Nevsky Prospect, next to the Church of the Nativity of the Blessed Virgin Mary, which was to be demolished after the new cathedral was built.
And so it was done after his death.
The consecration of the cathedral was timed to coincide with the coronation of Alexander I, which took place on September 15, 1811. But by that time the cathedral was not fully completed, so many of the architect’s plans were not realized: the colonnade of the southern facade was not built, the bell tower was not erected, two bronze angels were made of plaster and then removed from their pedestals without replacement. Similarly, the cast-iron fence and the drinking fountain in front of the cathedral’s entrance portico were left unfinished. A wooden obelisk was installed for the celebration.
At this point, the funds allocated for the project ran out, and Paul’s designs were unpopular with the new emperor, so financing stopped, and the temporary wooden structure remained standing. In 1813, the situation changed: relics of the victory in the Patriotic War were placed in the temple, so the obelisk even proved useful. Moreover, the structure served as a landmark, rising above the low buildings on Nevsky Prospect at that time.
How the obelisk was built is described in the book “Kazan Cathedral. Historical Research on the Cathedral and Its Description” by Andrey Aplaksin.

The obelisk was painted to look like granite and stood until the death of Alexander I; after his death, it was dismantled in 1826 as alien to Orthodoxy, so that the cathedral would less resemble the imitation of St. Peter’s Basilica in Rome.
Therefore, alas, Hyperboreans and reptiloids did not participate in the construction of the cathedral and the obelisk.
Sources:
A. G. Bulakh, By the Will of Reason and Feelings. Saint Petersburg — Helsinki: Two Orthodox Cathedral Churches, — St. Petersburg: Publishing House of St. Petersburg University, 2016
Aplaksin, A. Kazan Cathedral. Historical Research on the Cathedral and Its Description. St. Petersburg: R. Golike and A. Vilborg Printing Partnership, 1911.
Izmailovsky Garden, Fontanka River Embankment, 114, Saint Petersburg, Russia, 190005
Fontanka River Embankment, 2, Saint Petersburg, Russia, 191187
Admiralteysky Ave, 12, Saint Petersburg, Russia, 190000
Malaya Sadovaya St., 8, Saint Petersburg, Russia, 191023
Palace Square, 6, Saint Petersburg, Russia, 191186
Malaya Konyushennaya St., 16, Saint Petersburg, Russia, 191186
Moskovsky Ave., 19, Saint Petersburg, Leningrad Region, Russia, 190005
Razvodnaya St., 2, Saint Petersburg, Russia, 198510
Lieutenant Schmidt Embankment, 49, Saint Petersburg, Russia, 199034
Admiralteysky Lane, 1, Saint Petersburg, Russia, 190195
Petrovskaya Embankment, 6, Saint Petersburg, Russia, 197046
ter. Peter and Paul Fortress, 3, Saint Petersburg, Russia, 191186
Voskresenskaya Embankment, 12a, Saint Petersburg, Russia, 191123
Isaakievskaya Square, Saint Petersburg, Russia, 190000
nab. Reky Karpovki, 9, Saint Petersburg, Russia, 197022
Letter Z, Fontanka River Embankment, 132, Saint Petersburg, Russia, 190068
Grazhdansky Ave., 25 building 2, Saint Petersburg, Russia, 195220
k, Tikhoretsky Ave., 4b2, Saint Petersburg, Russia, 194064
Peter and Paul Fortress, Saint Petersburg, Russia, 197046
Universitetskaya Embankment, 11, Saint Petersburg, Russia, 199034
Lieutenant Schmidt Embankment, 9, Saint Petersburg, Russia, 199034
Liteyny Ave., 55 lit A, Saint Petersburg, Russia, 197372
Nevsky Ave., 17, Saint Petersburg, Russia, 191186
Vasilyevsky Island, 21st Line, V.O., Building 2, Saint Petersburg, Russia, 199106
Catherine Park / Ekaterininsky Park, Saint Petersburg, Russia, 196603
Devil's Bridge, Catherine Park, Saint Petersburg, Russia, 196609
Malaya Konyushennaya St., 5, Saint Petersburg, Russia, 191186
2 Tchaikovsky Street, Saint Petersburg, Russia, 191187
6a Pravdy St., Saint Petersburg, Russia, 191119
Saint-Germain Garden, Liteyny Ave., 46, Saint Petersburg, Russia, 191014
Manezhnaya Square, 4, Saint Petersburg, Russia, 191023
Kirochnaya St., 8, Saint Petersburg, Russia, 191028
Pinsky Lane, 1, Saint Petersburg, Russia, 197046
XGWR+7F Vsevolozhsk, Leningrad Oblast, Russia
Stachek Square, 1, Saint Petersburg, Russia, 190020
Revolyutsii Ave, 8, Saint Petersburg, Russia, 195027
195196, Stakhanovtsev St., 19, Saint Petersburg, Russia, 195196
Universitetskaya Embankment, 11, Saint Petersburg, Russia, 199034
Bering Street, 27k6, Saint Petersburg, Russia, 199397
Zagorodny Prospekt, 15-17, Saint Petersburg, Russia, 191002
23 Rubinstein St., Saint Petersburg, Russia, 191002
13 Pravdy St., Saint Petersburg, Russia, 191119
Ryabovskoe Highway, 78, Saint Petersburg, Russia, 195043
Building 28e, room 405, Khimikov Street, Saint Petersburg, Russia, 195030
Universitetskaya Embankment, 7/9, Saint Petersburg, Russia, 199034
Odessa St., 1, Saint Petersburg, Russia, 191124
Kronverkskaya Embankment, 3A, Saint Petersburg, Russia, 197046
Sytninskaya Square, 5A, Saint Petersburg, Russia, 197101
Apraksin Dvor, Saint Petersburg, Russia, 191023
Admiralteysky Canal Embankment, 2/3, Saint Petersburg, Russia, 190121
2 Zodchego Rossi Street, Saint Petersburg, Russia, 191023
Birzhevaya Square, 1 building 2, Saint Petersburg, Russia, 199034
Pulkovskoye Highway, 74, Saint Petersburg, Russia, 196140
Millionnaya St., 35, Saint Petersburg, Russia, 190000
Peter and Paul Fortress, Saint Petersburg, Russia, 191186
Island of Forts, Citadel Highway, 14, Saint Petersburg, Russia, 197760
Lieutenant Schmidt Embankment, 36, Saint Petersburg, Russia, 199034
Skippersky Lane, 10, Saint Petersburg, Russia, 199106
pl. Ostrovskogo, 1, Saint Petersburg, Russia, 191023
10th Sovetskaya St., 17B, Saint Petersburg, Russia, 191144
Volokolamsky Lane, 9, Saint Petersburg, Russia, 191119
Obvodny Canal Embankment, 102, Saint Petersburg, Russia, 196084