The main reason we wanted to make a trip to the Hill Country? Believe it or not, it was because my mom and I wanted to see the largest urban bat colony in the world... which just happens to be in Austin, Texas under the Congress Avenue Bridge.
The bats always emerge in the evening, sometime before dusk, to spend the night feeding on skeeters. Experts estimate that there are about one and a half million bats living under the Congress Avenue bridge (one of the city's bridges over the Colorado River). When they built the Congress Avenue bridge back in 1980, there were these approximately one-inch-wide crevices on the underside of the bridge. This happened to be just the kind of place that Mexican Free-Tailed Bats need, so they began moving in.
The headquarters of the newspaper (the Austin American-Statesman) actually owns the property from which the best views of the bats can be had. Being a good liberal rag, they set up a nice little viewing area for folks to congregate in each evening, so we doused ourselves with skeeter-spray and parked ourselves on the grassy knoll to await the bats.
And here they come!
They just poured out, appearing almost magically from the invisible crevices where they sleep during the day, and they kept pouring and pouring and pouring.
I have to say that this sight ranks way up there on my list of coolest things I ever saw in my life. I will never forget it, and if you come visit me I may insist on taking you down to Austin to see it. It's that cool.