In the inner end of the Bay of Vigo, beyond the Straight of Rande, are the islands of San Simón and San Antonio.
The islands —probably inhabited already in prehistoric times— witnessed, as a result of their strategic position, some of the most remarkable events in the history of Vigo and its Bay, as well as in that of the whole of Galicia.
The first known human settlement dates back to the High Middle Ages, around the fifth century AD, and was probably a small Monastery.
Between the twelfth and thirteenth centuries the Knight Templars settled on the islands. It is in this period that the first chapel of San Simón was built. Later, in 1370, the islands passed from the hands of the Crown of Castille and León to those of the bishopric of Tui.
Since 1507 the Monastery of the San Simón Island became the headquarters of the Order of the Pascualina Reform of the Holy Gospel up to the death of its founder in 1583. In 1585 the English pirate Sir Francis Drake attacked the Bay of Vigo and looted San Simón, only to return four years later, assaulting the island again and setting the Monastery in flames. San Simón was abandoned until 1602, when the Order of the Franciscans returned, rebuilding the constructions which had been destroyed before.
During the battle of Rande in 1702 the Monastery of San Simón was once again looted and burned down. Later, the order of St Benedict restored it and inhabited the island. In 1719 San Simón was attacked once more, pillaged and burned down, and the monks left the island. In 1842 the San Simón leper hospital began to operate, and for decades it was used as a quarantine centre for all vessels coming from America whose destination was any of the ports in Northwest Spain.