Saint Isaac's Cathedral or Isaakievskiy Sobor (Russian: Исаа́киевский Собо́р, romanized: Isaákiyevskiy Sobór) 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.