In this article, we propose a study of the construction process of the so-called “Dique” on the River Guadiana in Mérida. The analysis of the construction of this structure, which has traditionally been thought to be a containment wall for the river, has allowed us to pinpoint a series of aspects related to the architectural characteristics of the monument: the stratigraphy of the construction activities, the building techniques, the study of the structural elements, the use of different types of granite, the building phases, the technical resources employed and, in general, the organisation of the work.