Mycenae was founded between two tall conical hills, Profitis Ilias (805 m.) and Sara (660 m.), on a low plateau dominating the Argive plain and controlling both the land and sea routes. Grave Circle B, a stone-built funerary enclosure containing monumental graves with rich grave gifts, indicates that the first families of rulers and aristocrats appeared at Mycenae at approximately 1700 BC. This social structure developed further in the early Mycenaean period, c. 1600 BC, when a large central building, a second funerary enclosure (Grave Circle A) and the first tholos tombs were erected on the hill. The finds from these monuments show that the powerful Mycenaean rulers participated in a complex network of commercial exchange with other parts of the Mediterranean.