Historic Centre of Saint Petersburg and Related Groups of Monuments

Hello Today here is my second World Heritage site’s stamps from Russian Federation.
These stamps I just found in my collection. When I try to check about these stamps, I found that those are very historic stamps for World Heritage site of Russia ( Historic Centre of Saint Petersburg and Related Groups of Monuments)

Historic Centre of Saint Petersburg and Related Groups of Monuments is the name used by UNESCO when it collectively designated the historic core of the Russian city of St. Petersburg, as well as buildings and ensembles located in the immediate vicinity as a World Heritage Site in 1991.
First stamps features of Saint Isaac’s Cathedral and second stamps for Peter and Paul Fortress
Please read more about these WHS

Saint Isaac's Cathedral
Saint Isaac's Cathedral or Isaakievskiy Sobor (Russian: Исаа́киевский Собо́р) in Saint Petersburg, Russia is the largest cathedral (sobor) in the city and was the largest church in Russia when it was built (101.5 meters high). It is dedicated to Saint Isaac of Dalmatia, a patron saint of Peter the Great who had been born on the feast day of that saint.
The church on St Isaac's Square was ordered by Tsar Alexander I, to replace an earlier Rinaldiesque structure. A specially appointed commission examined several designs, including that of the French-born architect Auguste de Montferrand (1786–1858), who had studied in the atelier of Napoleon's designer, Charles Percier. Monferrand's design was criticised by some members of the commission for the dry and allegedly boring rhythm of its four identical pedimented octastyle porticos. It was also suggested that despite gigantic dimensions, the edifice would look squat and not very impressive. The emperor, who favoured the ponderous Empire style of architecture, had to step in and solve the dispute in Monferrand's favour.
The cathedral took 40 years to construct, under Montferrand's direction, from 1818 to 1858. Under the Soviet government, the building was abandoned, then turned into a museum of atheism. The dove sculpture was removed, and replaced by a Foucault pendulum. During World War II, the dome was painted over in gray to avoid attracting attention from enemy aircraft. With the fall of communism, the museum was removed and regular worship activity has resumed in the cathedral, but only in the left-hand side chapel. The main body of the cathedral is used for services on feast days only.


Peter and Paul Fortress
The Peter and Paul Fortress (Russian: Петропа́вловская кре́пость, Petropavlovskaya Krepost) is the original citadel of St. Petersburg, Russia, founded by Peter the Great in 1703 and built to Domenico Trezzini's designs from 1706 to 1740.

The fortress was established by Peter the Great on May 16 (by the Julian Calendar, hereafter indicated using "(J)"; May 27 by the Gregorian Calendar) 1703 on small Hare Island by the north bank of the Neva River. Built at the height of the Northern War in order to protect the projected capital, the fort never fulfilled its martial purpose. The citadel was completed with six bastions in earth and timber within a year, and it was rebuilt in stone from 1706 to 1740.
From around 1720, the fort served as a base for the city garrison and also as a prison for high ranking or political prisoners. The Trubetskoy bastion, rebuilt in the 1870s, became the main prison block. The first person to escape from the fortress prison (now an important destination for tourists) was the anarchist Prince Peter Kropotkin in 1876. Other people incarcerated in the "Russian Bastille" include Shneur Zalman of Liadi, Tsarevich Alexis, Artemy Volynsky, Tadeusz Kościuszko, Alexander Radishchev, the Decembrists, Fyodor Dostoevsky, Mikhail Bakunin, and Nikolai Chernyshevsky.