This collapsed grotto, which is surrounded by shady forests, has been turned into a swimming hole, complete with refreshing waterfall. It's also a short, 20-minute drive from Austin-- perfect for hipsters who want a swimming solution that's a little less mainstream. The grotto has a long history. It was once an underground river, until the dome collapsed due to erosion, forming the canyon-like pool we see today. Before the pool was owned by Morgon C. Hamilton, the area was inhabited by the…
