Most of the large Brazilian dams where developed in wide valleys. This condition led to the use of multiple types of structures in a single axis, such as embankments connected to spillways, intakes and other concrete structures. In Brazil, the most prevalent type of solution for such interfaces has been the use of a concrete gravity structure which is embraced by the embankment. However, other types of interface connection may be more efficient depending on the circumstances and the designer should look for the most efficient solution, which means an adequate water barrier with the least cost. This paper discusses the different types of interface geometry, comparing solutions employed in Brazilian dams. It focuses the most relevant geometric aspects of the concrete and earth structures and of filters/transitions in the contact, elements of utmost importance to avoid excessive flow and internal erosion of the core. The importance and limitations of field instrumentation of interfaces are evaluated. A comparison between gradients in different projects is provided to discuss how this parameter develops in such interfaces.