Heat created in this chamber (or in a firebox close by) is contained there and so builds up to high temperatures. The ceramic ware undergoes the firing and cooling process. While clay can be fired in an open fire and does not require a kiln, kilns must be used to attain high temperatures.
The Colorado Plateau, a series of flat lands, gorges, mountains and valleys, extends south into Arizona, and covers most of northern half of the state. The Black Mesa, Painted Desert, and Monument Valley in northeastern Arizona are some of the plateau's most interesting areas. Scattered tree-covered ranges of the Rocky Mountains wind through the Plateau, including the Black, San Francisco and White Mountains. Humphreys Peak is the highest point at 12,633 ft.
It is also the tallest building in the state of Arizona. The second-tallest building in the city and the state is the US Bank Center, which rises 407 feet (124 m). Of the 20 tallest buildings in Arizona, 18 are located in Phoenix. The history of skyscrapers in Phoenix began with the completion in 1924 of the Luhrs Building, which is regarded as the first high-rise in the city; the structure rose 138 feet (42 m) and ten floors.