South Austin, below the river

South Austin is everything below Lady Bird Lake and west of the interstate, and the close-in part of it, the 78704 ZIP code, has been the city's shorthand for itself for decades. Travis Heights climbs the hills east of South Congress Avenue around Blunn Creek, Bouldin Creek is the older grid west of Congress, and Zilker sits beside Zilker Park and Barton Springs. Further out the city was built later: Dove Springs, in the southeast, is subdivisions along Williamson Creek, and Circle C Ranch, in the southwest, is a planned community the City annexed over its residents' objections on 18 December 1997. 5 guides are listed below.

The creeks decide more here than anywhere else in the city. Onion Creek flooded hundreds of homes on the southern edge of Dove Springs on 31 October 2013 and again in October 2015, and the City has bought out and cleared hundreds of houses in the Onion Creek floodplain since. The City now regulates to rainfall figures that moved many more houses into the 100-year floodplain, so the flood map for an exact address is the first thing to read anywhere near a creek. West of MoPac and south of the river much of this area also drains to Barton Springs over the Edwards Aquifer, where the Save Our Springs Ordinance limits how much of a lot can be paved or built on, which is a large part of why Circle C looks the way it does.