North America’s 8 Best (and Secret) Swimming Holes … Hamilton Pool, Texas Our second Texas swimming hole, comes by way of the Hamilton Pool grotto. This historic pool is located just 45 minutes outside Austin. In the summer it can get very busy so best to get there early. Also, you definitely want to call or check to see if it's open. I visited in September of 2014, drove all the way there and it was closed due to some clean up they were doing.