period, there were two-story dwellings made primarily of stone masonry, the presence of towers, and family and community kivas. Pueblo III (). Rohn and Ferguson, authors of Puebloan ruins of the Southwest, state that during the Pueblo III period there was a significant community change. Moving in from dispersed farmsteads into community centers at pueblos canyon heads or cliff dwellings on canyon shelves. Population peaked between 1200 and 1250 to more than 20,000 in the Mesa Verde region. By 1300 Ancient Pueblo People abandoned their settlements, as the result of climate changes and food shortage, and moved south to villages in Arizona and New Mexico. Architecture The ancient population centers such as Chaco Canyon, Mesa Verde, and Bandelier for which the Ancestral Puebloans are renowned consisted of apartment-like complexes and structures made from stone, adobe mud, and other local material, or were carved into the sides of canyon walls. The structures contained within these alcoves were mostly blocks of hard sandstone, held together and plastered with adobe mortar. Specific constructions had many similarities, but were generally unique in form due to the individual topography of different alcoves along the canyon walls. Decorative motifs for these sandstone/mortar constructions, both cliff dwellings and otherwise, included T-shaped windows and doors. Construction characteristics Most notable Pueblo structures were made of adobe and built like an apartment complex. Generally speaking, Pueblo buildings feature a box base, smaller box on top, and an even smaller one on top of that, with the tallest reaching four and five stories. There were floors for storage and defense, living and religious ceremonies. Generally, there were no doors on the bottom floor until recent times. This limited access to the buildings so movable ladders were key elements. One ladder would take inhabitants to the patio, or second floor, and another led through an opening through a roof and onto the first floor. Other ladders led to higher floors. Architectural elements The key technology of the Pueblo peoples was their irrigation techniques. These were used throughout their dwellings, and often determined the siting of communities. Many pueblos feature T-shaped doors in adobe walls. Usually one meter wide, they are wider on top and narrower below. The Great house-style pueblos were constructed on a box system. Builders used molds to pour compacted mud without organic material. The exterior was stuccoed with sand, lime and oyster dust shells, then it was painted blue,