The San Antonio Zoo is located at the headwaters of the San Antonio River -- just minutes from the Alamo and the Riverwalk. Artesian water flows through the Zoo grounds, an abandoned rock quarry where tall oak, pecan, and bald cypress trees provide cool summer shade. Limestone cliffs surround the naturalistic enclosures and make dramatic backdrops for many of the animal habitats. Along the riverbank, humid, tropical conditions prevail, while a short distance away, semi-arid hillsides dominate. San Antonio's temperate climate makes it possible to keep most animals in outside enclosures year round.