Saint Isaac's Cathedral or Isaakievskiy Sobor is a large architectural landmark cathedral that currently functions as a museum with occasional church services in Saint Petersburg, Russia. 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. It was originally built as a cathedral but was turned into a museum by the Soviet government in 1931 and has remained a museum ever since, with church services held in a side chapel since the 1990s. In 2017, the Governor of Saint Petersburg offered to transfer the cathedral back to the Russian Orthodox Church, but this was not accomplished due to the protests of St Petersburg citizens opposing the offer.

Vincenzo Brenna was an Italian architect and painter who was the house architect of Paul I of Russia. Brenna was hired by Paul and his spouse Maria Fyodorovna as interior decorator in 1781 and by the end of 1780s became the couple's leading architect. Brenna worked on Pavlovsk Palace and Gatchina palaces, rebuilt Saint Isaac's Cathedral, and most notably created Saint Michael's Castle in Saint Petersburg. Most of his architectural works were created concurrently during Paul's brief reign. Soon after Paul was murdered in a palace coup Brenna, renowned for fraud and embezzlement barely tolerated by his late patron, retired and left Russia for an uneventful life in Saxony.