The greatest group of architectural remains on this continent is that of the Maya region, mainly in Yucatan. For a full description of many of these buildings the reader is referred again to the admirable work of Maudsley. The Mayas were the greatest architects as well as the greatest artists and greatest in almost everything of all the Amerinds, and if Goodman is correct in his rendering of some of their chronology they occupied the region more than ten thousand years.[215] Mound-like foundations supported the buildings, which generally rose as from a terrace, though sometimes the mound was very high and very steep, with small space around the building crowning it. At Copan,[216] which was in ruins before the Spaniards arrived, there is a great main terrace from which mounds rise, the latter bearing the buildings. The casing of the mound and the walls of buildings are of nicely dressed oblong stones usually without mortar. The joints were not broken here, nor in other Maya work. The mound slopes were terraced at five-foot intervals and the steps were about five feet high. The so-called “triangular arch” probably existed here as it did at the other Maya ruins. It was made by advancing the courses, several feet above the base of an opening, gradually toward each other till they met above, where a large slab was usually laid across to bind the whole together. The ceilings or roofs of many rooms in Maya ruins were wholly made this way. It has also been called a corbel arch, though it is, in fact, not an arch at all. See illustrations, pages 210, 235, and 237. There was no arch in Amerindian architecture besides the one the Eskimo constructed in his snow hut. The rooms are generally long and narrow in all the Maya structures and no windows existed. The Maya inability to span wide spaces was the cause of the narrow rooms and buildings. At Uxmal the two main rooms of the so-called Governor’s Palace are sixty feet long and only eleven to thirteen feet wide. The walls of all the structures are very thick, though certain walls, as the rear ones, are usually thicker than the others and have no openings, the latter, as a rule, being along one, two, or three sides. This was a probable survival of earlier defensive constructions similar to the communal fortresses of the Puebloan type as particularly exemplified in the ruins of the Chaco in New Mexico, where there were no rear openings. See ground plans, page 232. At Palenque are some fine examples of the Maya construction. The largest is called the palace and is 180 feet wide, 228 feet long, and 25 feet high, with fourteen doorways on the side and eleven at the ends. It was one story in height, as were all Maya buildings. There is a vast amount of carving and stucco modelling around them. One of the most unique constructions is that called the “Temple of the Cross,” number one, or two, or three, by different explorers, there being two structures much alike. See note 2, page 184. This is on top of a high