The towers of Mount Jaizkibel are the main evidence of the military activity that took place in the area during the 19th century. Six towers were built along the entire ridge of the Jaizkibel mountain range, and the remains of five of them can still be seen today. Three of these towers are located in the summer resort of Lezo and are listed as a Monumental Complex. Looking south from them, the entire Irun-Pasaia corridor can be seen, while looking north, the slopes of Mount Jaizkibel, descending towards the sea.
They were built during the last Carlist period (1872-1876), since as soon as the military actions of the Carlist troops threatened Irun, its City Council requested the Government to build several defensive works. By Order of 8 April 1873, authorization was granted to build the defensive works in Irun, provided that they were carried out in accordance with the instructions of the Corps of Military Engineers.
All the towers have a hexagonal base, measuring between 3.3 and 3.5 m on each side, except for the one closest to Guadalupe, which has a square base. They all had two floors and a terrace. Today, only the perimeter sandstone walls are preserved, and the interior is completely empty. On the lower floor, there were some right-angled slits, which were used to ventilate and observe the interior of the tower.
On the outside, they had a base, slightly wider than the tower itself, and whose height from the ground depended on the unevenness of the ground. The access to the tower was not on the ground floor, but on the first, and if necessary, it was accessed by a staircase that could be removed or hidden if necessary, to make access more difficult. On this floor, on the other hand, there were two or three slits on each side. The terrace is slightly advanced in relation to the facade, supported by three wings or projections on each side of the polygon and another at each vertex. Each of these wings has a circular hole through which rainwater can drain.
