At the time of the Christian Reconquest of the Iberian peninsula, the town and its castle were first conquered or by troops under the command of D. Afonso Henriques (1112-1185) or by the group under the command Geraldo Sem-Pavor in raid promoted in 1166 the territory beyond the river Guadiana.

He returned to the Muslim possession when the great offensive Almohad Abu Yusuf Ya’qub al-Mansur to the river Tagus (1191), when Christians remained in power only of Évora, in the Alentejo. Later, the forces of King Sancho II recover these lands, with Serpa won in 1232 and its areas delivered to Ferdinand, brother of the sovereign.

The castle stands in the center of the village, the two hundred and thirty meters above the sea level. At the highest level, by the wall on the north deploys to fortress, of square plan.

About the village has oval plant, reinforced by turrets and square and semicircular plant towers, topped by merlons prismatic. It was originally tore three monumental gates (Moura Gate, northeast, Beja Port, northwest and Seville port south, the latter now defunct) flanked by two beveled round towers, these merlons with pentagonal shot. The west cloth of the walls is topped by an aqueduct based on arcade go round, joining the Counts of Palace Ficalho, on the north side and a giant daughter based on a well, next to the southeast angle, built in the seventeenth century to supply the palace. In period opened the Door of Corredoura and the New Port.

The wall of the fortress is reinforced by the Keep, of square plan, adjoining south cloth, left to bottom; by a semicircular plant cubelo the same side and a rectangular plan tower in the southeast corner, next to which is still visible part of the Barbican involved. There is installed the Archaeological Museum of Serpa, exposing the evidence recovered in County region, the Paleolithic, Neolithic, of the Metal Age and Roman times.

In the square border to the Church of Santa Maria (old Muslim Mosque) stands the so-called Clock Tower, of square plan, where stands the bell, with tapered shot of pinnacles surrounded by merlons bevelled. Trace the fence of the village, was transformed into watch in 1440, becoming the third watch tower oldest in the country.

Its original building dates back to the fourteenth century, probably having been performed on an ancient Arab mosque.

Outside, it highlights the impressive entrance portal and its side pillars, which support two images of St. Peter and St. Paul. Sports, still, a bell square tower on the left. The current structure of the quadrangular bell tower houses inside an old cylindrical structure, which may have been the ancient minaret mesquita.

The interior consists of three naves, divided by arches supported by columns. The side chapels have examples of gilt, witnessing the decorative richness of the Baroque. The main chapel, dominating the whole set, the date of the sixteenth and seventeenth centuries. In the remaining decoration, stand out even a statue of Our Lady of Fatima, images of Christ and other vegetal, animal and human elements.

The Muslim core, called the Castelo Velho “Old Castle”, corresponds to the oldest district of the metropolis, distinguished by irregular flatness of the streets. It was here that the Arabs built the fortress and its mosque, whose foundations would be located where the Christian power built the Church of Santa Maria.

With the final conquest of low-Alentejo town in 1230, won by Templar troops, the urban fabric of Serpa get to know a gradual development. Finally, it regained in 1242 in the reign of D. Sancho II and settled in 1295 by King Dinis, during which it is designed the first charter, restoring the castle and builds a large curtain walls, who took part the walled structure of the Islamic citadel.

This rectangular enclosure corresponding to the walls, was gradually occupied by medieval houses. However, the fourteenth century has brought a slowdown in growth, and only in the late fifteenth century and during the sixteenth century, the growing population center, expanding out of the walls, with the creation of the parish of Salvador. This period is again renovated the castle.

The enclosure of medieval walls, although currently severely damaged can still be rebuilt.

Serpa was already populated before the domain of the Romans, however these were that fomented the county, especially at the farm level. In 1166 it was conquered from the Moors by D. Afonso Henriques, and was lost several times in the constant struggles of the Reconquista.

It was definitely established as a county by D. Dinis, who also sent rebuild your castle and Serpa surround by a ring of walls, in 1295.

Its location, close to the Spanish border, caused serious problems for the development of this county. In the Wars of Restoration, Serpa was almost completely destroyed, including its stronghold.

The park includes the municipalities of Mértola and Serpa, located district of Beja, covering the waterfront of the Guadiana River and the Mértola village, town of great historical interest.

The Guadiana Valley Natural Park was created to protect part of the Guadiana river section and the surrounding plain, is one of the driest areas of the country, with an average annual rainfall of 600 mm. The south, between Castro Marim and Vila Real de Santo António, lies one marsh area, which acts as a “nursery” for juvenile fish and an important refuge for many species of birds.