Just ten miles southeast of Fredericksburg is a deserted railroad tunnel, home to up to three million bats. The tunnel, decommissioned in 1941, is home to mostly Mexican free-tailed bats, as well as around 3,000 Cave myotis. Each night, from May to October, just before and during sunset, the bats pour out of the tunnel in massive droves, spiraling to upwards of 10,000 feet. The bats will travel up to 60 miles in search of insect prey, and can reach speeds of up to 60 mph.

The bat emergence at Old Tunnel Wildlife Management Area (WMA) can be seen from either an upper viewing area, which is free, or from a lower viewing area, which has an admission fee but includes a tour guide. The upper viewing area is best utilized during August and September, when the bats emerge earlier and can be better observed. Red-tailed hawks can be seen diving into the plume of bats, snatching them out of the air in mid-flight.

The tunnel itself was bored out of “Big Hill”, as the locals call it, about 920 feet through rock. The work was started in April 1913, and by August the first train had passed through the tunnel. Old Tunnel was carved in order to bring the railroad to Fredericksburg, which had unsuccessfully attempted to bring the rail to town many times.

Unfortunately for the old German settlement, the railroad was not destined for their town, and the automobile would soon make their recently finished line obsolete. In 1941 the owners of the line sold off much of the rails, ties, and timbers, which ended up in a variety of places including the Alcan Highway to Alaska.