Austin is the capital of the state of Texas, within the United States of America. As of Census 2000, the population of 656,562 people (metro area population of over 1 million people) made Austin the fourth-largest city in Texas (behind Houston, Dallas, and San Antonio), and the 17th largest in the U.S. Austin is the county seat of Travis County and is situated in Central Texas. Austin was founded in 1835 and was first named Waterloo. In 1838, Mirabeau B. Lamar renamed the city in honor of Stephen F. Austin. Its original name is honored by local business establishments such as Waterloo Ice House and Waterloo Records. Austin is also the home of the University of Texas at Austin, aka "UT," the flagship campus of The University of Texas System. Other institutions of higher learning include Austin Community College, Concordia University, Huston-Tillotson College and St. Edward's University. Austin has a heady mix of educators and their students, politicians and lobbyists. It is also the self-proclaimed "live music capital of the world," with a vibrant live music scene revolving around many nightclubs on 6th Street and a yearly film/music/multimedia festival known as "South by Southwest." Austin City Limits, the longest-running concert music program on American television, is videotaped on the University of Texas campus. Austin is situated on the Colorado River, with three lakes within the city limits: Town Lake, Lake Austin, and Lake Walter E. Long. Additionally, the foot of Lake Travis, including Mansfield Dam, is located within the city's limits. Town Lake, Lake Austin, and Lake Travis are all on the Colorado River. The city is also situated on the Balcones Fault, which, in much of Austin, runs roughly the same route as the MoPac expressway. The eastern part of the city is flat, whereas the western part and western suburbs consist of scenic rolling hills on the edge of the Texas Hill Country. Because the hills to the west are primarily limestone rock with a thin covering of topsoil, the city is subjected to frequent flash flooding from the excessive runoff caused by thunderstorms. To help control this runoff and to generate hydroelectric power, the Lower Colorado River Authority operates a series of dams that form the Texas Highland Lakes. The lakes also provide venues for boating, swimming, and other forms of recreation within several parks located on the lake shores. The Congress Avenue Bridge houses the world's largest urban bat population. In the summer, the colony has up to 1.5 million Free-tailed Bats; in the winter they migrate to Mexico. At night, Austin is lit with "artificial moonlight." Several Moonlight Towers, built in the late 19th century and recognized as historical landmarks, illuminate the central part of the city. The towers were prominently featured in the film Dazed and Confused. The Zilker Tree is a Christmas tree made of large lights strung from the top of a moon tower. It stands all year in Zilker Park and is lit in December along with the Trail of Lights. Among the professional sports teams in Austin are the Austin Ice Bats of the Central Hockey League and the Austin Wranglers of the Arena Football League. Austin is served by the Austin-Bergstrom International Airport. Residents of Austin are called "Austinites."