San Antonio, Texas
Mission Concepción, or Misión de Nuestra Señora de la Purísima Concepción de Acuña, is renowned for its well-preserved colorful frescoes. It is the oldest unrestored stone church in America, standing essentially as it did when completed in 1755.
The mission is famous for a solar event that occurs on the Feast of the Assumption, where the sun illuminates the altar and face of the Virgin Mary. This architectural alignment demonstrates the sophisticated engineering skills of the Spanish friars.
As part of the San Antonio Missions National Historical Park, it is a UNESCO World Heritage Site. The mission continues to function as an active Catholic parish, hosting regular services within its historic walls.