Andrei Kvasov (1718–1772), trained by Mikhail Zemtsov, was one of St. Petersburg’s principal architects. In 1743-1744 he presented Empress Elizabeth with his design of the expansion of Catherine I’s residence. He also included a model of the future palace. According to Kvasov’s design, two semicircular service wings – circumferences – were to flank the older building. At Tsarskoe Selo, Kvasov was assisted by the architect Giuseppe Trezzini (1670–1734); the latter was replaced in May 1745 by a renowned Savva Chevakinsky who supervised the palace construction till the early 1750s.