The oldest unrestored stone church in the United States, completed in 1755. Mission Nuestra Señora de la Purísima Concepción de Acuña sits on a bend of the San Antonio River about three miles south of downtown, its twin bell towers rising above the pecan trees. Unlike the restored missions, everything here is original — the stone, the mortar, the arched doorways — which gives it a weathered authenticity the others lack.
Part of the San Antonio Missions UNESCO World Heritage Site. The National Park Service maintains it with minimal intervention. Free entry; ranger-led tours on weekends. The walk between Mission Concepción and Mission San José along the Mission Reach trail takes about an hour.