Kizhi Island

Absolutely incredible!  Kizhi is this little island on Lake Onega that is entirely devoted to an outdoor, open-air "museum" of wooden architecture.  There are 2 main churches (the Cathedral of the Transfiguration and the Cathedral of the Intercession) and a bell tower as the main attractions, which were all built from wood without a single nail.  A little further on is the chapel of the Archangel Michael, rumored to cure dental ailments if you rub up against the walls, and the oldest wooden building in Russia - the Church of the Resurrection of Lazarus.

Mosquitos abound everywhere, though.  Beware.