Twenty-one of the roof beams in Spruce Tree House have been dated by tree-ring chronology. These dates show that the houses were constructed during the years between 1230 A.D. and 1274 A.D. In 1276 A.D. a 24-year period of drought began that caused the cliff dwellers to move to regions where there was a more permanent supply of water. In those same regions are the homes of the modern Pueblo Indians and no doubt some of these people are the descendants of the cliff dwellers. CLIFF PALACE Cliff Palace lies in an eastern spur of Cliff Canyon under the roof of an enormous cave that arches 50 to 100 feet above it. The floor of the cave is elevated about 200 feet above the bottom of the canyon and is just under the rim of the mesa. The entrance of the cave faces west, toward a great promontory upon which stands Sun Temple. The total length of the cave is over 300 feet and its greatest depth is just under 100 feet. The vaulted roof is so high that the cave is always light and airy, offering a perfect home site to the cliff dwellers who were seeking protection from the elements as well as from their enemies. Fortunately, the configuration of the cliffs above the ruin makes it possible to get a fine bird's-eye view from the rim of the mesa. Views obtained from the heads of the two trails are most striking and give an idea of the setting and size of the building before it is entered for closer inspection. The most spectacular view of Cliff Palace is from Sun Temple, across the canyon. This is the only spot from which the entire ruin may be seen. LIVING ROOMS Cliff Palace is the largest known cliff dwelling. Dr. Fewkes, who excavated the ruin in 1909, placed the number of living rooms at slightly more than 200. Very few of the walls reached the top of the cave because of its great height, but many of the structures were as high as two and three stories. Near the south end of the ruin is the tallest structure, a four-story tower that reaches the cave roof. Ground space appropriate for building purposes was at a premium in the cave. To provide for an increasing population, second-, third-, and even fourth-story rooms were superimposed on the original single-story structures which predominated in the initial cliff-dweller occupation of this site.