Complex sentence: Close to the main entrance to the beach town is located the "Valley Tower", from the 17th century, its surroundings are now used as a leisure area, it was part of the mediterran watchtowers net.
Split into simpler sentences: Close to the main entrance to the beach town is located the "Valley Tower", from the 17th century. Its surroundings are now used as a leisure area and it was part of the Mediterranean watchtowers net.