South of Marathon, there's a rock formation called Rainbow Cliffs, which has served as a landmark for centuries. The striated rock gave protection to Camp Pena Colorado, a Buffalo Soldier encampment as well as the native peoples gathering at the nearby spring and its water. To read more about history and geology of the spot, click here.
You can see Rainbow Cliffs and visit nearby WPA project, Post Park on our heritage bike route (an easy 10 miles total, out-and-back) which can also be driven. Post Park is also a site on our Far West Texas Wildlife Trail map on the Marathon-Alpine loop! Check it out!