Summer is an excellent time to travel but be prepared for more tourists in the major cities. Museums may be a little crowded but it is nothing in comparison with the crowds in Venice or London for example.
Water isn't of the same standard as water in Western Europe and the USA.
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There are a lot of handicrafts that can be purchased that are intimately related to Russia: nesting dolls, lacquered boxes, traditional Russian outfits - sarafans and head-dresses kokoshniks, wood carving and painted figurines, khokhloma wood crockery and many other nice souvenirs.