On several occasions, San Sebastian had to defend its jurisdiction over the port of Pasaia against the claims of the new towns which had sprung up in the area around the strategic port. In the first half of the sixteenth century a roughly circular tower was built on the west bank, occupied until 1805 by a governor-tower-keeper with jurisdiction over the access canal and the inlet. To supplement the limited artillery which could be installed in the tower itself, a gun platform was erected some distance away. The building was damaged by fire in 1835, and finally demolished in 1867.

23. Plano de la Ría y Puerto de los Pasages y de las Poblaciones situadas en su Costa según se hallaban en el año de 1760, charted by the military engineer Felipe Cramer (fragment).© Carlos Mengs