Great Springs Trail Race - Natural Bridge Caverns

The Great Springs Trail Race at Natural Bridge Caverns is a last-one-standing race on a 4.1667-mile loop north of San Antonio. A lap goes off every hour, on the hour, from the race hub arch on the surface. Get round inside the hour and you earn the right to start the next one, and whatever time you save is yours to eat, sleep or sit in. The race director blows a whistle twice at five minutes to the hour and once to send the field away. It ends when one runner is left who can still make the loop in an hour.

The Last Person Standing starts at 7:00 a.m. and has no cutoff, because there is nothing to beat except everyone else. Finish a 24th lap and the organiser upgrades your caverns tour pass, which is the closest thing the race keeps to a milestone.

The shorter races on the same day start underground. The 4, 8 and 16 mile fields run a quarter-mile section inside Natural Bridge Caverns itself, part of the Comal Caverns network, before surfacing into hills and wooded trail. Last Person Standing runners do not go through the cave and are given a tour pass to use whenever they like. A ruck division runs its own 2.47-mile loop and is scored as its own last-one-standing.

A 4.1667-mile loop for the Last Person Standing, starting and finishing at the race hub arch on the surface, with a lap sent away every hour on the hour. The ruck division runs a 2.47-mile loop and is scored separately. The 4, 8 and 16 mile races start with a quarter-mile section inside the caverns and are scored on chip time rather than the gun time this organiser uses everywhere else, because those fields go underground in groups assigned by check-in time. They clear the course at 1:30 p.m., after which it belongs to the Last Person Standing alone. The race publishes no elevation figure. Its winners history begins in 2025.

First-come sign-up on RunSignUp, with no lottery, no qualifying standard and no published cap on the Last Person Standing run; the ruck division is capped at 245 places and the 16 mile at 105. Entry for September 2026 opened on November 21, 2025 and closes at 9:30 a.m. on race morning. The Last Person Standing is $140 from December 1, 2025, $150 from June 29, 2026, $160 from September 2 and $190 for the last nine days. Entry comes with a 10% discount code for the caverns tours and the ropes course.