Watch what happens when rocks fall at Cliff Palace. This is from August, when we closed down tours to spall off loose rocks above Cliff Palace. All of these sandstone alcoves are unstable, and small pieces often fall. When bigger rocks threaten, we try to knock them loose. Sometimes, the threatening rocks are so large that we have to close down whole alcoves. That's why Spruce Tree House is closed this year. (sdb) | Mesa Verde National Park