The plan of the castle, in the shape of an irregular triangle, adapts to the plateau of the Cerro de San Marcos, it is inclined to the east and naturally steep to the north.

The La Guardia castle enclosure is structured in two individualized and well-defined spaces: the fortress and the fortress.

Located in the northwest corner of the enclosure, is the fortress, a late 15th-century work, renovated and ornamented in the 16th century. It has a rectangular plan and is defended by four towers of different physiognomy, a circular tower, two square towers and the keep, which are adapted to the orography of the land. It is surrounded by canvases of wall made of masonry joined by lime mortar and reinforced corners, sometimes rounded, with rope ashlar masonry.

The circular tower, located in the southwest corner, is an Islamic construction built in masonry, from which two sections of the wall are made with mud brick on a masonry base. It has a structure with three levels: The first two habitable, are covered by two half-orange vaults and communicate with each other through a staircase embedded in the wall of the tower. The intermediate room also had openings that allowed traffic and communication between towers and walkways.

In the southeast corner we find another tower, with a square plan and small dimensions, covered with a barrel vault.

The tower that occupies the northeast end has a rectangular plan structured in two levels, the lower one has been greatly altered by recent restorations, and the upper one covered with a pointed barrel vault with transverse arches.

Finally, the extreme northwest was defended by the Tower of Homage, about 35 meters high, which has a square plan divided into three sections. The lower level is massive and adapts to the geological rock on which it rests. The second level is covered by a gabled vault, configuring an internal space with an octagonal floor plan, with several loopholes, currently transformed into viewing balconies. The third level and the crenellated terrace were accessed through a staircase embedded in its walls and covered with small barrel vaults. The room that opens on the third level was covered with a ribbed vault, illuminated by four openings or loopholes.

Inside the fortress there are two wells nestled in the southernmost sector, from different periods and were built with different construction techniques. One, from the Islamic period, built in mud of lime and gravel, and the other, attached to the previous one and built during the Castilian conquest, we find thick masonry walls.

The walled enclosure of the citadel dates from the 13th century. The walls have a zigzag or rack layout that makes the addition of towers for their defense unnecessary. On the north side there was only a parapet overlooking the escarpment.

In the entire route, there is only one tower built on the eastern canvas, destined to defend the access door to the complex. To access the fortress, a path was created that, attached to the walls, reached the vicinity of the gate, and once it was crossed, one entered a closed space with a rectangular plan, which prevented direct access to the interior enclosure.

The main entrance to the fortress was through a monumental late Gothic door, built in the 16th century. The door, decorated with the weapons of Mexía Carrillo, is of great beauty and originality, and gave access to a large parade ground that in medieval times would house the sparse population of the place or a large part of it.

In the parade ground are the remains of the parish church of Santa María, built in the 16th century, rectangular in shape, with six side chapels, and its apse takes advantage of the only tower that existed in the entire walled enclosure of the citadel. A new bell tower is attached to this building.

Apart from these buildings for residential and palatial use, the archaeological excavations carried out inside the complex have documented a series of outbuildings built in the 16th and 17th centuries, such as warehouses, warehouses, transit yards, corridors and kitchens, the objective of which was that of providing the Castle-Palace with service areas.