Located just east of Town, Swift Creek Canyon is just a few minutes drive from Town. During the summer when the spring is most active, visitors will be able to witness Afton's main water source intermit in 15 minute cycles. The half hour hike up to the mouth of the canyon is well worth the visit for residents and tourists alike.
To date no one has been able to prove conclusively why the spring intermits. A leading theory by a hydrologist from the University of Utah theorizes that the spring discharges spring runoff from the mountain when enough water has been collected, creating a siphon effect of sorts. The spring is located at the end of a scenic gravel road in the Swift Creek Canyon, approximately five miles east of Afton.
Fore more info: http://www.aftonwyoming.net/