The Cathedral's 122.5m-high bell tower is the second structure in St Petersburg after the television tower. At the base there is a small exhibition about the renovation of the tower in 1997, as well as an up-close inspection of the bell-ringing mechanism. The main reason to climb all these steps, of course, is for the magnificent 360-degree panorama.
Tickets for guided tours (in Russian only) are sold at the boathouse information centre; if you're happy to look around on your own then buy your ticket inside the cathedral.
