You will stay at The Mosaic Courtyard opposite to the Summer Garden.
ALL major sights of St. Petersburg are within walking distance:
The Summer Garden - 3 min
The Peter and Paul Fortress 17 min
The Hermitage and The Palace Square 18 min
Mikhailovsky Castle 13 min
The Russian Museum 19 min
The Church of the Savior on Spilled Blood 16 min
Main theatres (The Mikhailovsky Theatre 20 min), circus (14 min) and 3 restaurant streets are nearby.
Shopping: Gostiny Dvor, The Passage and Nevsky Prospekt.