The hike starts at the Spanish Bottom trailhead. A short distance out, about 140 - 150 yards, you'll see a trail that leads off to the right. Taking this turn will have you hiking in a counter-clockwise loop out to the ancestral Puebloan granary. The hiking is easy, on soft sand, and you weave through the colorful rock formations known as the Doll House. Pay attention for cairns as there are numerous social trails that can lead you astray. You'll soon come near what appears to be a solid rock wall. However, just before wall the trail takes a hard right turn and through a narrow opening through the spires of the Doll House.
Once through the opening you descend into a small walled valley (aka a graben). You descend further into the valley by passing through a "slot" in the rock that, at one point, forces you to remove your pack to get through. Continue on the trail and arrive at a sign pointing you in the direction of the granary (to the right). The trail then gently ascends and affords you great views of Surprise Valley (a much larger graben) on your left. After leaving the canyon rim of Surprise Valley, you hike for another 2 - 3 minutes to reach a small alcove. Within the alcove are the prehistoric granaries. The one on the right is a single "storage unit", while the one on the left is 3 units built together.
From the alcove you head back the way you came to the sign for the granary. Along the way you'll be able to see the Colorado River. You could completely retrace your steps by taking a left at the sign or, as I did, take a right and make a loop using the Spanish Bottom trail. The trail connecting the granary sign and the Spanish Bottom trial is about 1/4-mile long and descends towards Spanish Bottom (a flat, broad, sandy area in Cataract Canyon of the Colorado river). You'll shortly come to another grouping of signs. From here you take a left and pick your way among the slickrock and boulders to ascend back to your starting point. If you take a right at the group of signs, you can switchback your way down to Spanish Bottom . I'd suggest that if your legs are tired from previous hikes that you conduct this loop in a clockwise fashion so you don't have the moderately steep ascent at the end.
Check out the Official Route.