Isaakievskii Sobor (St. Isaac's Cathedral)

The panoramic view this place can offer you of the city is astounding. The interior of the church is also very classy and elegant without being too Byzantine and over the top like a lot of the other Russian Cathedrals. The stained glass windows are beautiful. Conveniently located in the center of town, it is also an ideal tourist site for those with mobility problems, although they won't be able to enjoy the catwalk.