At the first major segment junction in Doble Mensula

The galleries of Doble Mensula are relatively broad, due in large part to the special roofing structure (Doble Mensula = double corbel or double cantilever) that gives the gallery its name. These massive projections just below the ceiling allow the stone roofing beams to span a gap narrower than the entire gallery width. On the end of the segment leading to the surface is a relatively narrow doorway: this is a gateway originally built as part of the south facade of an earlier version of the Castillo. In the last major Castillo expansion it was incorporated into the Doble Mensula gallery and became an underground feature.