Austin, Texas map

Austin lies almost exactly in the center of the Texas Triangle, 80 miles northeast of San Antonio, 165 miles southwest of Houston (via US-290) and 195 miles south of Dallas. I-35 runs north–south straight through downtown, separating the older west side from East Austin. Austin is the largest U.S. city with no interstate running east–west; US-290, US-183 and the SH-71/Ben White corridor do that job instead.

The city spills into Williamson County to the north and Hays County to the south. Lake Travis and Lake Austin, both dammed sections of the Colorado River, form the northwestern edge of the metro.

Travis County, which held 1,290,188 people in 2020 across 1,025 square miles, is the fifth-most populous county in Texas and contains almost all of the city. The Balcones Fault crosses it from southwest to northeast, close to the line of MoPac and I-35: west of the fault is the Edwards Plateau, limestone hills cut by creeks; east of it is the Blackland Prairie, dark farm soil that flattens toward Bastrop. The county's other neighbors are Caldwell to the south, Blanco to the west and Burnet to the northwest.

The Colorado River, 862 miles long and the longest river contained entirely within Texas, crosses Travis County from west to east and is the reason the city stands where it does. Six dams built by the Lower Colorado River Authority turned the stretch above and through Austin into the Highland Lakes: Lake Buchanan, Inks Lake, Lake LBJ and Lake Marble Falls upstream in Burnet County, then Lake Travis behind Mansfield Dam and Lake Austin behind Tom Miller Dam. Lake Travis is the flood-control reservoir of the chain, which is why its level swings by tens of feet between drought and flood while the lakes above it stay near constant.

Inside the city the river is Lady Bird Lake, a narrow pool held back by Longhorn Dam east of downtown. Motorboats are barred from it, so it carries rowing shells and kayaks, and the hike-and-bike trail that circles it runs about ten miles. South of the water, Barton Creek feeds Barton Springs in Zilker Park, an Edwards Aquifer spring that stays near 68°F year round; its recharge zone is the hill country southwest of town, which is why building there is regulated so closely.

The Texas State Capitol was finished in 1888 at the head of Congress Avenue, about eleven blocks north of the river, on a 22-acre square. It is built of sunset red granite quarried at Granite Mountain near Marble Falls, and the state paid for it not in cash but with three million acres of Panhandle rangeland that became the XIT Ranch. The Capitol Complex of state office buildings runs north from the grounds toward the University of Texas.

Because the dome is the fixed reference point of the city, the state and the city adopted Capitol View Corridors in the 1980s: a set of protected sightlines from bridges, streets and parks around Austin, each of which caps how tall a building along it may be. That is why the downtown towers stand in clusters with gaps between them rather than in a solid wall, and why the dome is still visible from the south end of the Congress Avenue bridge.

Austin–Bergstrom International Airport is about five miles southeast of downtown, reached from SH-71 and US-183. It occupies the site of Bergstrom Air Force Base, which closed in 1993; the airport opened on the base in 1999 and still uses its runways. The city's previous airport, Robert Mueller Municipal, closed the same year, and its runways became the street grid of the Mueller district in East Austin.

Most of the metro's growth has run north up I-35 into Williamson County, which reached 609,017 people in 2020. Round Rock (119,468) and Georgetown (67,176), the county seat 30 miles north of the Capitol, anchor that corridor, with Cedar Park, Leander and Pflugerville filling the gaps between them. South of the county line, Hays County and San Marcos take the overflow toward San Antonio.