The evidences of ancient human occupation in the Bandelier neighborhood are apparent even to the most casual observer. When driving over the approach road to the monument headquarters one cannot fail to observe cave rooms in the cliffs on every hand; the continuing spectacle of smoke-blackened chambers dug into the rock provides the stimulus of discovery en route. But the roadside introduction is an infinitesimal preview of the total scope of prehistoric man’s activity in the region. In actuality, all of the ruins contained within the national monument represent but a small fraction of the ruins of the surrounding plateau. [Illustration: _Park ranger and visitors at the Big Kiva in Frijoles Canyon._] The entire eastern slope of the Jemez Mountains to the west, throughout the zone of moderate elevations from 7,000 feet down to the Rio Grande at 5,500 feet, appears to have been thickly settled in prehistoric times; this eastern slope has been given the name of Pajarito Plateau. The extent of the plateau is, very roughly, 30 miles north to south, and 10 miles east to west (from the Rio Grande west to the crest of the Jemez). From Santa Clara Creek on the north of the monument to the Canada de Cochiti on the south of the monument, this tract of forested mesas and canyons contains Indian ruins which, if not innumerable, at least at this writing have not yet been totaled. It perhaps may be said, to emphasize the concentration of these ruins, that an observant person can hardly walk a quarter of a mile in any direction through the once-inhabited zone without noticing some sort of ancient structure or handiwork of prehistoric man. [Illustration: _Base of a cliff of volcanic tuff, showing several cave rooms._] The habitations of the early people were of two types, basically: the cliff or cave dwelling, and the masonry or open pueblo structure. But these two types were frequently blended into composite dwellings, part cave and part masonry, wherein a cliff formed the back wall of the building. It is this third type, called a talus house, which is conspicuous along the canyon sides within and near the national monument. The rock which forms the walls of all the Pajarito canyons is a cemented volcanic ash called tuff, with many erosion cavities which can be readily enlarged with tools of hard stone. It might be logical to assume that early migrants to the Pajarito country, 700 years ago, first took shelter in the natural cavities, then presently improved these crude holes into more livable chambers. There is, however, no evidence to support the idea that the cave rooms were lived in first. In fact, some authorities reason that since the firstcomers had been living in masonry dwellings in their earlier homes, they would first have built the familiar communal buildings on arrival here, leaving the caves to be taken up later by overflow population.