Nearly 300 small sports equipment and outdoor wear shops. You can find ski's, weights, bikes, clothes and fishing gear here. It is quite chaotic, so be sure to take your time and check out all 3 levels to find what you're looking for.
Map of the center: http://www.extreme-shop.ru/plan.htm
How to get there: http://www.extreme-shop.ru/location.htm
Location: 63b Smolnaya Ulitsa, near Rechnoy Vokzal metro station