Austin is very outdoorsy, so hiking is plentiful. Lady Bird Lake for people-watching, Barton Creek Greenbelt for feeling like you're alone in the woods (well, more alone). Lake Travis for boating or similar.
6th street for watching drunk people, but pick up the free weekly "Austin Chronicle" for the best places to see live music.
South congress ave south of the river for window shopping and trailers serving variety of food. Rent a bike if you are physically able—parking and traffic can be challenging.
Uchi for 4 star sushi (at **** prices).
Canoe/kayak rental on town lake at zilker park.
Barton springs pool in zilker park—spring-fed, year-round water temp 68*F.
Broken spoke for country music/dancing.
Any particular interests you want to explore? over 5 years ago