During this tour all sights of St. Petersburg are available (both from inside and outside): 

The Church of the Saviour on Spilled Blood, The Cathedral of Our Lady of Kazan, Saint Isaac’s Cathedral, The Peter & Paul Fortress, St. Nicolas Church, The Church of Dormition, the Yusupov Palace on the Moika River, the Smolny Cathedral, the Cruiser Aurora, the Summer Gardens of Peter the Great, the University Embankment and many other interesting sights. 

The tour usually lasts for 3-4h

Nevsky Prospect – the main avenue of St.Petersburg

The University Embankment

The Church of Dormition on the Basil Island

View of the Spit of Vasilyevsky Island from above