Mértola

The last two thousand years:
During the Migration Period, Mértola was invaded by Germanic tribes of the Sueves and the Visigoths. In this period (5th-8th centuries) commerce was reduced but still active, as evidenced by Greek tombstones from the 6th-7th centuries found in Mértola which suggest the presence of Byzantine merchants in the town.
During Classical Antiquity, Mértola was inhabited by Phoenicians, Carthaginians and finally the Romans, who called it Myrtilis Iulia. The strategic location of Mértola, on a hill by the northernmost navigable part of the Guadiana river, was crucial in its early development. Agricultural products grown in the villae nearby and valuable minerals (silver, gold and tin) obtained from the lower Alentejo region were sent from the fluvial port of Mértola via the Guadiana to Southern Hispania and the Mediterranean. The town was raised to the status of a Municipium in times of Emperor Augustus and was connected to important Roman cities (Beja, Évora) through a road system.
Mértola had a wall dating from Roman times, but the Muslims built new fortifications and, eventually, a castle to protect it from rival Muslim and Christian states. After the fall of the Caliphate of Córdoba, in 1031, Mértola became an independent taifa state, until it was conquered by the taifa of Seville in 1044-1045. Between 1144 and 1150 the town was again seat of an independent state led by Ibn Qasi, a mystic and skilled military leader who unified Southern Portugal and fought the power of the Almoravides. The independence of the region, however, was soon ended by an invading Almohad army. The most important remnant from the Islamic period of Mértola is its mosque, built in the second half of the 12th century and later turned into a church, but which still preserves many of its original characteristics.
In 1238, in the context of the Reconquista, the town was conquered by Portuguese King Sancho II, putting an end on centuries of Islamic domination in the Mértola region. The town was donated to the Knights of the Order of Santiago, a Military Order that played a vital role in the Christian conquest of Southern Portugal.