Attending a service at this incredible cathedral, with its remarkable artwork, soaring choral voices, powerful scent of incense and the seriousness and ritual of the proceedings, is truly a feast for the senses and an absorbing experience, whatever your religious or (in my case) non-religious leanings. This historic landmark is packed to the rafters with colorful frescos, drop-dead stained glass, classic Russian icons and has got to be one of the most beautiful in the city.