The Order of San Julián del Pereiro, which was founded in 1176 on Portuguese soil, changed its name to the Military Order of Alcántara in 1218. The Order played an important part in the Reconquest, during which extensive territories were annexed to give it an important economic and military position. In the early 16th century a Royal Privilege was granted for the construction of the new building which was to be the headquarters of the Order of Alcántara. Work was initiated during the reign of the Catholic Monarchs in 1505 and continued until 1574 under the direction of various architects including Pedro de Larrea, who was responsible for the construction (during the final Gothic period) of the cloister and some surrounding rooms. Pedro de Ybarra, who worked in the second half of the 16th century, by then in the plateresque period, built the church and the guest quarters. On the east façade can be found the Gallery of Charles V, which was part of the guest quarters of the monastery. Its structure is divided into three storeys and it is flanked by two cylindrical towers, one of which bears the coat of arms of Charles V and the other that of Philip II. The unfinished church which is dedicated to the Immaculate Conception is of Renaissance design; it consists of three naves with ribbed vaults. Two coats of arms of Charles V dominate the central nave; the side ones correspond to the chapels of the Knight Commanders Diego de Santillán and Nicolás de Ovando. In the transept, which is on one side, opens out the chapel of the Knight Commander of Piedrabuena, Antonio Bravo de Jerez, and the other contains the vestry with its original spiral stairway. In what was formerly the kitchen garden of the monastery, a auditorium was constructed which serves as the setting for the Alcántara Classical Theatre Festival.