Nimrud took the lead with 75,000 people by 800 B.C.
Located in Iraq at a strategic point on the Tigris River, Nimrud was the capital of the Neo-Assyrian Empire.
In the ninth century B.C., King Ashurnasirpal II built a huge palace made of "cedar, cypress, juniper, boxwood, mulberry, pistachio wood, and tamarisk" filled with art and treasure. He also built temples, botanical gardens, and a zoo.
King Shalmaneser III, his son, would go on to build a palace that was twice as big.