English: Structure 17, also called The Twins. is located to the west of the South Plaza and is one that contains the best architectural characteristics at Ek' Balam. It is formed by a large foundation upon which two others were built to support two vaulted buildings of four rooms each. The structure measures 40 m. long, 17 m. wide and is approximately 6 m. high.

The decorations of the facades of the buildings of Ek' Balam were not done with carved figures in the stones - as at Uxmal and Chichen Itza - but with stucco or limestone mortar, modeled into distinct forms and painted. During the excavation, two stucco masks were found which formed part of the decoration. The only decorative stone elements in this building are the small hoops which are in the corners of the rooms.

Beneath the building, which we can now appreciate, there are two structures which were completely covered: it was the custom of then ancient Maya architects to use structures from earlier periods as the foundations for the construction of new buildings.