Provided in both Spanish and English, these professionally produced audio tours highlight items of interest throughout the four Missions in the UNESCO World Heritage Site. Visitors may access the tour for free by using their cell phones. The Mission Heritage Partners oversees the tour content and maintains the signs indicating the phone number and tour selection at several waypoints throughout the Park. In addition to being available at the four San Antonio Mission sites in the National Historical Park, the audio tour is available at the Espada Aqueduct and Espada Dam. Access to the tour is particularly helpful to visitors when staff and volunteers are unavailable.