The town of Lerma, in Burgos, stands on a hill overlooking the valley of the Arlanza river. It is a town where we can find the remains of medieval walls and a ring of convents, churches and manor houses, of which the Palacio Ducal deserves to be mentioned, a treasure of the Herreran style and witness to the flourishing past once lived by this town, in the times of King Felipe III.

Lerma, declared a Historic and Artistic Site in 1965, is one of the most harmonious cities of Herreran style and amongst those erected in the first third of the 18th century it is the one where the architecture has been most respected. Also, part of the popular local architecture and the signs of former times and cultures have been preserved over the ages.

There are many places from which to start a tour around the Villa, which will surprise the tourist with the amount of monuments on display. Before beginning the tour of ducal Lerma one must go back further in time to discover the impressive Roman bridge with its seven arches that is on the outskirts of town. The Arco de la Carcel (the Prison Arch) is one of the four entrance gates that remain from the old medieval walls.