In 1352, then emperor Caxtoltzin moved the city from the mainland to the island of Tlilan. In this respect it was like another island city in the area, Tenochtitlan. Although no longer an island, the city center is still in the same spot. In 1376, Tenochtitlan attacked Xochimilco, forcing the city to appeal to Azcapotzalco for help. The conquest was unsuccessful, but Xochimilco was then forced to pay tribute to Azcapotzalco. Tenochtitlan succeeded in conquering Xochimilco in 1430, while it was ruled by Tzalpoyotzin. Shortly thereafter, Aztec emperor Itzcoatl built the causeway or calzada that would connect the two cities over the lake. During the reign of Moctezuma Ilhuicamina, the Xochimilcas contributed materials and manpower to construct a temple to Huitzilopochtli. They also participated in the further conquests of the Aztec Empire such as in Cuauhnáhuac (Cuernavaca), Xalisco and the Metztitlán and Oaxaca valleys. For their service, Ahuizotl, granted the Xochimilcas autonomy in their lands, and the two cities coexisted peacefully. Aztec emperors would pass by here on royal barges on their way to Chalco/Xico, then an island in Lake Chalco. For centuries Xochimilco remained relatively separate from Mexico City but provided much of the larger city's produce.