With labor from Indigenous South Texans, the Spanish built five missions on the northern frontier of New Spain. Four of the five comprise San Antonio Missions National Historic Park, and all five missions, including Mission Valero, are UNESCO World Heritage Sites. They are the most complete and intact group of Spanish Colonial mission complexes in the world. Through these mission communities, the Spanish asserted political, religious, and cultural influences on newly claimed territories. All four missions within the park are active parishes. Mission Concepción is home to the best-preserved mission church and contains the largest single collection of Spanish Colonial frescos in the nation. Mission San José, the largest of the missions, includes a church, native quarters, a mill, and a granary within its walled complex, and a 1930s project restored much of the church and other structures. At Mission San Juan, the standing building, visible ruins, and reconstructed walls convey the scale of the mission complex, while walking trails offer views of the San Antonio River and the historic farmlands and irrigation system. Mission Espada includes the historic mission complex, and two miles north lies the Espada Aqueduct, the only functioning aqueduct from the Spanish Colonial period in the United States.