According to Guiness World Records, the largest set of Russian dolls is a 51-piece set hand-painted by Youlia Bereznitskaia (Russia). The largest measures 1 ft 9.25 in (53.97 cm) in height, the smallest 0.125 in (0.31 cm) in height. The set was completed on 25 April 2003.
When all 51 pieces are lined up together touching, they measure 11 ft 2.25 in length. To break this record both the number of dolls in the set and the height of the tallest must be broken.
The other giant Matryoshka doll you see in what appears to be somekind of town center is actually in Taowa Square in Manzhouli, China. The doll in the center is 100 feet high and presides over a square full of matryoshka-themed souvenir shops. Sounds like heaven to me, except for the part about it being in Mongolia.