The Inka used architecture as a means to subjugate local populations, transforming physical space to express power and domination throughout Tawantinsuyu. Emblematic Inka structures are identifiable by their perpendicular geometry, their solid rectangular form, their imposing height and well crafted masonry. Trapezoid doorways, windows and niches are also typical. Inka settlements were centered around a large rectangular area enclosed by walls, called a kancha, inside which they built structures that served different functions. The kancha also had a central plaza-like area that the buildings within the enclosure opened onto. Walls were crafted with incredible skill in stone and adobe, while the A-framed straw and mud roofs were supported by wooden beams. Noteworthy among Inka buildings were the immense kallankas, as well as kollkas, ventilated food storehouses, usually built in airy places. The ushnu was a ritual Inka platform of great ideological importance. The vast territory of Tawantinsuyu was united by the Capac Ñam or Inka Road, which boasted complex engineering works such as bridges and stone staircases. Tambos, located at regular intervals along the road system, served as way stations and offered rooms and corrals. The Inka settlements of Chile were often built apart from local villages, indicating the Inka’s intention to differentiate themselves from the local population. Just south of Santiago, there are three Inka pukaras (Chena, Chada and Cerro Grande de la Compañía), located strategically on hilltops with panoramic views of the valley below. These sites served the Inka as forts as well as emblems of their authority, and mark the southernmost reach of Tawantinsuyu. Their military function also points to periods of conflict between the Inka and the local population.