The majestic fortresses belong to a more recent period; these were built to defend the island from the pirate attacks and other civilizations due to its strategic location in the centre of the Mediterranean. These fortresses were built, almost entirely, at the Maó harbour, the main entrance of enemy fleets. One can admire the Mola fortress along the coast (19th century), the Sant Felip Castle with its underground tunnels, which can still be visited today, and Fort Marlborough (built by the British in the 18th century).
As we travel around the island, we will encounter the watch towers or defence turrets built at strategic sites with elevations and good visibility, along the coast or inland, in order to communicate between themselves by alarm signals and, therefore, avoid being invaded. In order to learn the towers' uses and the island defence system between the 16th and 19th century, we can visit the exhibition at the Torre de Fornells.