Inca rule rested on the ayllu, a kin-based community holding land in common, and the mit'a, a rotating labour tax owed to the state in place of money or goods. Households took turns to serve fixed spells on state projects, building and maintaining roads, terraces, irrigation, storehouses and monumental centres, and to staff armies and mines. The state in return fed and supplied workers from its stores, casting obligation as reciprocity. Whole settlements of relocated mitmaq colonists were planted to secure new lands and build infrastructure.
Mit'a and ayllu were the institutional engine that produced the Inca built environment, from the Qhapaq Ñan to planned administrative cities. They constitute a non-monetary mode of mobilising the labour that makes large-scale urbanism possible.