Saint Isaac's Cathedral or Isaakievskiy Sobor (Russian: Исаа́киевский Собо́р) in Saint Petersburg, Russia is the largest Russian Orthodox cathedral in the city. 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 neoclassical exterior expresses the traditional Russian-Byzantine formula of a Greek-cross ground plan with a large central dome and four subsidiary domes. It is similar to Andrea Palladio's Villa La Rotonda, with a full dome on a high drum substituted for the Villa's low central saucer dome. The design of the cathedral in general and the dome in particular later influenced the design of the Wisconsin State Capitol in Madison, Wisconsin and the Cathedral in Helsinki.
The exterior is faced with gray and pink stone, and features a total of 112 red granite columns with Corinthian capitals, each hewn and erected as a single block: 48 at ground level, 24 on the rotunda of the uppermost dome, 8 on each of four side domes, and 2 framing each of four windows. The rotunda is encircled by a walkway accessible to tourists. 24 statues stand on the roof, and another 24 on top of the rotunda.
The meticulous and painstakingly detailed work on constructing the St. Isaac's Cathedral took 40 years to complete, and left an expression in the Finnish language, rakentaa kuin Iisakin kirkkoa ("to build like St. Isaac's Church"), for lengthy and never-ending megaprojects.
