Built in the 13th century, this circular tower protected the northern entrance to the Llanes wall. It has a ground floor and three floors, and an access door built in the reform of the 1950s directed by Luis Menéndez Pidal. At the time it had a moat and drawbridge for access. It currently houses the tourist office. It was declared a National Monument in 1876 (the first monument declared as such in Asturias).

It is part of the preserved section of the Llanes wall, which runs from the old pass that connected the Sablón beach with the church to the San Nicolás gate, next to the Santa Ana chapel (section that now delimits the Casa del Cercáu).