Pueblo de Taos is the largest living multi-storied pueblo structure in the U.S., and it appears today much as it did when Spanish explorers arrived in New Mexico in 1540. The structure of the Pueblo is a study unto itself. The walls are made of thin layers of mud and straw, the outside layers of which weather away quickly and must be continually replaced. Tightly packed dirt covers a framework of aspen and large timbers to create the roofs of each of the 5 stories. The Pueblo today does include fireplaces, exterior doors and windows as the people living there no longer need to blatantly protect themselves from warring neighbors, or other menacing forces. However, Tribal custom allows no running water or electricity. Two hundred Taos Indians live in the Pueblo full-time. Graciously, the public is invited to certain ceremonial dances held throughout the year.