The Zerain jail or dungeon was built, together with the town hall, in 1711 when, in addition to other services, a facility of this kind was sorely needed.
One of the jail's most interesting features is the oak panelling on the walls.
Since the stones used to build the walls were joined together by mud, it was very easy for prisoners to loosen a few and escape. The walls were therefore covered with a wooden framework in order to lessen the possibilities of escape.
Visitors today can also see the stocks and shackles used to restrain the more dangerous prisoners. Although some prisoners were not bound at all, others were tied standing against the wall or confined on the floor by a set of giant stocks.
Over the years, the jail has played host to all kinds of 'visitors', including 26 prisoners of war brought to the region in 1835 to work in the mines. During the 20th century, the jail gradually fell into disuse, and it is now preserved as a unique record of our past, being the only surviving 16th century jail in Gipuzkoa.
The Zerain jail played host to two different types of prisoner: those serving only a few days for petty theft or drunkenness, and those condemned for more serious crimes such as robbery and smuggling.
For the latter, the Zerain jail was no more than a temporary stopping point, since these prisoners served their sentences onboard galleys in the Bay of Biscay. The royal road which ran through Segura was once one of the most common routes to the coast, and the prisoners and their guards would often stay the night in the Zerain jail or other similar places along the way.