The document describes the Peter and Paul Cathedral located in St. Petersburg, Russia. It provides details on the cathedral's location on Zayachy Island in the center of St. Petersburg, where it was originally built as a protective fortress in 1703 by Peter the Great. The cathedral later became the burial site for the Romanov dynasty and remains an important historical and architectural landmark from the 18th century. Visitors are invited to join a tour to explore and learn more about the famous fortress and cathedral.