At the corners of the four pediment porticos of the cathedral, twelve sculptures are installed. They were created between 1842 and 1844 based on models by Ivan Petrovich Vitali (1794–1855), with the participation of L. Bouilly. Three figures on the northern pediment are made of copper using the galvanoplastic method at the Duke of Leuchtenberg’s factory, while the other nine were cast in bronze and chased at Berd’s factory.

The bas-relief of the western portico, "Isaac Blesses Emperor Theodosius," is constructed with strict symmetry and a calm rhythm. Here, alongside conventionally interpreted characters, I. P. Vitali created realistic images, endowing them with features of his contemporaries. For example, the portraits of the nobles Victor and Saturninus bear a resemblance to Prince P. M. Volkonsky, chairman of the Commission for the Construction of Saint Isaac’s Cathedral, and A. N. Olenin, president of the Academy of Arts. In the left corner of the bas-relief is a sculpture in an antique toga holding a model of Saint Isaac’s Cathedral, with an Egyptian statue at its feet—a hint at the connection between European architecture and ancient cultures. This is indeed a portrait of Montferrand, clearly recognizable by his features and proportions. Vitali created a unique portrait of the architect, depicting him among a group of saints and contemporaries. Moreover, all the characters bow their heads in greeting to Saint Isaac of Dalmatia, except Montferrand, who holds his head upright. Montferrand personally supervised the work on this and other elements of the cathedral—and knew perfectly well that one of the characters was suspiciously recognizable. Montferrand could have agreed to the detail, overlooked it, or even approved it—there are no documents that definitively interpret this episode.

Portraying himself in such a setting was, in itself, a rather bold move. But more than that, he died a month after the consecration of Saint Isaac’s Cathedral. The mysterious death of the architect, which was also predicted, gave rise to the most fantastic guesses and rumors. According to legend, during the solemn consecration of the cathedral, either the emperor or one of Alexander II’s close associates drew the tsar’s attention to the sculptural group of saints on the temple’s pediment. Among them was a sculpture of Montferrand himself holding a model of the cathedral. Portraying himself in such a setting was, in itself, a rather bold move. 

Noting the architect’s pride to himself, the emperor allegedly did not shake his hand or thank him for his work, which upset Montferrand, who fell ill and died. In reality, Montferrand died from an acute attack of rheumatism following pneumonia. He bequeathed to be buried in Saint Isaac’s Cathedral, but the emperor did not consent. Montferrand’s widow took the architect’s body to Paris, where he was buried in Montmartre Cemetery.

Inside the cathedral stands a marble bust of the architect. The unusual multicolored bust was created by the young sculptor Antonio Folletti during the architect’s lifetime, in 1850. Folletti depicted the 64-year-old Montferrand at the height of his fame—with imperial orders of Saint Equal-to-the-Apostles Prince Vladimir and Saint Anna, the Legion of Honor (France), and the Order of the Red Eagle (Prussia). The portrait is executed in stone carving technique, using mosaic assembly, with at least nine types of stones used in the building’s decoration (a technique employed by Italian masters of the Renaissance). The architect’s face is carved from white Carrara marble, hair from gray Bardiglio marble, uniform from gray granite, collar of the uniform from aspid slate, cloak from Shokshin raspberry quartzite, order ribbon from green Genoese marble, and the orders from yellow Sienese marble and raspberry quartzite. The bust’s pedestal is made of pink Tivdian marble. For this work, the Imperial Academy of Arts awarded Antonio Folletti a gold medal.

Sources:

https://pantv.livejournal.com/4046435.html

Commons.wikimedia.org/ A. C. Tatarinov

https://ru.wikipedia.org/wiki/%D0%A4%D0%B0%D0%B9%D0%BB:Saint_Isaac%27s_cathedral_west_front_%28SPb%29.jpg#file

https://cathedral.ru/ru/isaac/outersculpture#:~:text=По%20углам%20фронтонов%20установлены%20статуи,на%20востоке%20Лука%20с%20тельцом.

https://love-gorod.ru/saint-petersburg/obj/isaakievskiy-sobor

https://spb.aif.ru/city/event/ispolin_na_bolote_pyat_legend_isaakievskogo_sobora