Tulsa is located in the northeastern corner of Oklahoma between the edge of the Great Plains and the foot of the Ozarks in a generally forested region of rolling hills. The city touches the eastern extent of the Cross Timbers, an ecoregion of forest and prairie transitioning from the drier plains of the west to the wetter forests of the east. With a wetter climate than points westward, Tulsa serves as a gateway to "Green Country", a popular and official designation for northeast Oklahoma that stems from the region's green vegetation and relatively large number of hills and lakes compared to central and western areas of Oklahoma, which lie largely in the drier Great Plains region of the Central United States. Located near the western edge of the U.S. Interior Highlands, northeastern Oklahoma is the most topographically diverse part of the state, containing seven of Oklahoma's 11 eco-regions and more than half of its state parks. The region encompasses 30 lakes or reservoirs and borders the neighboring states of Kansas, Missouri, and Arkansas. The geographic coordinates of the city of Tulsa are 36°7′53″N 95°56′14″W (36.131294, −95.937332), with an elevation of 700 feet (210 m) above sea level.
The city developed on both sides of the prominent Arkansas River, which flows in a wide, sandy-bottomed channel. Its flow through the Tulsa area is controlled by upstream flood control reservoirs, but its width and depth can vary widely throughout the year, such as during periods of high rainfall or severe drought. A low-water dam was built to maintain a full channel at all times in the area adjacent to downtown Tulsa. This portion of the river was known as Zink Lake. However, the City of Tulsa allowed the dam to deteriorate and it no longer functions to retain the lake for which it was designed.
Heavily wooded and with abundant parks and water areas, the city has several prominent hills, such as "Shadow Mountain" and "Turkey Mountain", which create varied terrain, especially in its southern portions. While its central and northern sections are generally flat to gently undulating, the Osage Hills extension into the northwestern part of the city further varies the landscape. Holmes Peak, north of the city, is the tallest point in the Tulsa Metro area at 1,360 ft (415 m) According to the United States Census Bureau, the city has a total area of 186.8 square miles (484 km2), of which 182.6 square miles (473 km2) is land and 4.2 square miles (11 km2) (2.24%) is water.