West of the sawgrass prairies and sloughs lies the Big Cypress Swamp, commonly called "The Big Cypress", referring to its size rather than the height or diameter of its trees. It takes up the majority of Collier County; at its most limited measurement, the swamp measures 1,200 square miles (3,100 km2), but its hydrological boundary is nearly twice as large.[55][56] The Big Cypress is slightly elevated at 22 feet (6.7 m) at its highest point and slopes gradually to the coastline for approximately 35 miles (56 km). Because the defining feature of The Big Cypress is the abundance of trees it is considered a swamp, rather than a marsh where grass is the main characteristic.