Detail from Rassam Obelisk found at Kalhu showing tribute being weighed in front of Ashurnasirpal II (king of Assyria from 883 to 859 BC). Mesopotamian weights were based on the sexagesimal system. Sexagesimal (base 60) is a numeral system with sixty as its base. It originated with the ancient Sumerians in the 3rd millennium BC, it was passed down to the ancient Babylonians, and it is still used, in a modified form, for measuring time, angles, and geographic coordinates. The palaces, temples and other buildings raised by Ashurnasirpal II bear witness to a considerable development of wealth and art. He was renowned for his brutality, using enslaved captives to build a new Assyrian capital at Kalhu (Nimrud) in Mesopotamia where he built many impressive monuments. He was also a shrewd administrator who realized that he could gain greater control over his empire by installing Assyrian governors rather than depending on local client rulers paying tribute.