A few meters from the baroque door that gives access to the church is the Royal Gate, wedged between two towers whose appearance is reminiscent of the Serranos Towers of Valencia. This access leads to the interior enclosure that groups all the rooms of the monastery itself, that is to say, to the real enclosure. It is surrounded by a defensive wall built by Pedro IV, who ordered a space in the church to be set aside for a royal pantheon to guard the bones of the most glorious kings of the House of Aragon. The works were directed by his lieutenant, Friar Guillén de Agulló, and the wall, which has a perimeter of 608 meters, 11 meters high and 2 meters thick, has battlements, loopholes and a walkway, being defended by 12 polygonal towers. Two of these towers flank the Royal Gate, while those on the corners were used as prison towers; among them are the tower of the Hosts, adjacent to the new sacristy, the tower of the Fools in the northeast direction and others called the Prior, the Oil, the Corner, the Arms, San Esteban, the Shoemaker and the Cardinal.

The Royal Gate is a military construction of the XIV century, in which the hollow of the door presents an arch of average point with great voussoirs; in its keystone, an angel sustains the shield of the Crown adorned with two rampant lions. On both sides there are bells of King Pedro IV, and on one of them one can read an inscription in Latin that indicates that the work began in the time of this monarch. Above the door, the royal shields alternate with that of Abbot Guillermo Agulló, builder of the door between 1361 and 1393.

Once through the Royal Gate, the visitor finds on the left the vestiges of what were the rooms of converts and donators, while on the right some stone stairs lead to the palace of King Martin the Humane, built at the beginning of the 15th century and now used as a museum. Opposite the Royal Gate is the atrium or vestibule of the cloister, the work of Abbot Copons, and to its left are the cellars, which originally served as a dining room for laymen or converts; over this building was built in the fourteenth century the dormitory of retired monks, where in 1983 the museum of the restoration of the monastery was installed.

To the right of the atrium are the 13th century wine presses, which were originally the dormitory for laymen, while the south wall is adjacent to the north wall of the church. Inside the atrium is the corner of the confluence with the north-west side of the cloister. To the east of the walled enclosure are the oldest facilities, dating from the 12th century, such as the chapel of San Esteban and the infirmary; in addition, in this area are located the Royal Chambers, built in the 14th century on the wall, and in the northeast corner were built the modern rooms for retired monks.