Russia - St Isaac's Cathedral in Saint Petersburg

This postcard also arrived in the Slavic countries & Rest of the world RR (I don't think it's cheating, when people agree to send each other 2 postcards, is it?) ;)
It shows the St Isaac's Cathedral (Исаакиевский собор) in Saint Petersburg.

Saint Isaac's Cathedral or Isaakievskiy Sobor 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 was 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 has closed 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.