Dinotopia was made up of a main island, and a much smaller one called the Outer Island. There were also many other smaller islets and reefs. Dinotopia's capital city was Sauropolis. The "main island" was approx. 240 miles (385 kilometers) in length, and approx. 260 miles (420 kilometers) in breadth. In the center of the "main island" was the Rainy Basin, which with the Great Desert made up most of the island. These two land-marks were separated by the Forbidden Mountains, a huge range that intersected a smaller mountain range called the Backbone Mountains. A truly spectacular place was Waterfall City; It was built in the middle of the Polongo River, a large river that held all the water from the Rainy Basin.