Natural swimming pool filled entirely by nearby natural springs. The water is (REALLY) cold, but it's worth a dive. Located within Zilker Park. Bring $8 to enter if you're an out-of-towner ($3 if you're a local).
Kayaks and stand-up paddle boards on Lady Bird Lake in Downtown Austin. No reservations needed, but be sure to bring your driver's license along with you to rent a boat. Tours are given Friday morning (book below).
Congress Ave Bat Bridge
Map | 305 S Congress Ave, 78704 Bat Scoping | Website
Join hundreds of others and huddle on the hill right below Congress Street Bridge to watch a show of a lifetime! Thousands of bats have claimed home underneath the bridge. At dusk each night, they leave their stoops for a feeding frenzy. It's an unbelievable sight.