The square is located in the historical center of the city next to St. Isaac's Cathedral, the composition includes a monument to Nicholas I. The monument was the first equestrian statue in Europe with only two points of support, and thanks to this engineering feature it was not destroyed during the Soviet era. The facades of the Astoria Hotel, considered the most comfortable hotel in St. Petersburg since its opening, and the Angleterre Hotel, where S. Yesenin's life was tragically cut short, face St. Isaac's Square. The Blue Bridge, one of the "colored" bridges and the widest bridge in St. Petersburg, spans the Moika River near St. Isaac's Square.

During the siege of Leningrad, vegetables were grown in the flowerbeds of the square.

Near the Blue Bridge, near house 44 on Bolshaya Morskaya Street, there is a water meter with marks of the levels of the largest floods in the history of the city. The largest flood was in 1824: the water rose by 421 cm. There is also a sundial installed on the pole.