Designed by the architect Auguste Montferrand, the Cathedral of the venerable St Isaac the Dalmatian represents an outstanding monument of the 19th century Russian architecture. Its grandeur is evident through its dimensions: it is 101.5 m high, 111.2 m long and 97.6 m wide.
The Cathedral is one of the city’s architectural landmarks and the second tallest structure after St. Peter and Paul Cathedral. Its grand and magnificent outlines feature prominently in the skyline, serving as a symbol of the Northern capital, along with the spire of St Peter and Paul Fortress, the Bronze Horseman, and the gilded weathervane of the Admiralty.
The Cathedral is based on a church design developed in the late 18th century - a five-domed, rectangular, centrally planned structure with facades decorated with porticos.
The edifice is conceived as a solid, compact cube mounted with a high cylinder drum that is punctured with arched windows and surrounded with an elegant colonnade. The drum is topped with a light octagonal lantern.
Placed at the projecting corners of the main body are four smaller bell towers that nicely complement the silhouette of the Cathedral. These are topped with light gilt cupolas proportionate in size to the towers and, therefore, appear much smaller than the main dome. The undisturbed surface of the walls is pierced with arched windows adorned with massive casings and volutes above. One-third of the upper façade is taken up with the enormous attic, which excessively dominates over the main orb.
St Isaac’s Cathedral is the only structure in the Russian Neo-Classical style (with the exception of the Marble Palace by A. Rinaldi) that incorporates polished granite columns and marble in its exterior decoration. The spectacular combination of the dark red portico columns, the colonnade around the main dome, the cathedral’s base with grey marble veneers and the gilded domes emphasizes the grand appearance of the entire structure.
St Isaac’s Cathedral is a remarkable example of the unity between monumental and decorative forms of art.