The Peter and Paul Fortress is the original citadel of Saint Petersburg, Russia, founded by Peter the Great in 1703 and built to Domenico Trezzini's designs from 1706 to 1740 as a star fortress. Between the first half of the 1700s and early 1920s it served as a prison for political criminals. It has been a museum since 1924.

Saint Petersburg, formerly known as Petrograd and later Leningrad, is the second-largest city in Russia after Moscow. It is situated on the River Neva, at the head of the Gulf of Finland on the Baltic Sea. The city had a population of roughly 5.6 million residents as of 2021, with more than 6.4 million people living in the metropolitan area. Saint Petersburg is the fourth-most populous city in Europe, the most populous city on the Baltic Sea, and the world's northernmost city of more than 1 million residents. As Russia's Imperial capital, and a historically strategic port, it is governed as a federal city.