The Castle of Sant Joan was built between the 11th and 13th centuries. The first time it was heard of, it was the year 1001 and it belonged to the Viscount of Cabrera. We find it located at the top of the Sant Joan hill and it has a height of 173 meters above the sea, a characteristic that allows a panoramic view of the entire city of Blanes.The Castle of Sant Joan was built to monitor the maritime incursions of pirates, especially in times when the kingdom of Mallorca was under Arab rule. This castle offered the population of Blanes a safe place when the invasions came.It was formed by a walled enclosure 23 meters wide and 34 meters long, but the element that stands out the most is the tower with a cylindrical base 15 meters high. From the 15th century, together with the palace of the viscounts, it formed part of a great axis of fortifications that have been called the line of the castles of Tordera. These fortifications, which began in Montseny and ended in Blanes, had the mission of protecting the city of Barcelona from the north.