The Mas building is located in “Call”, Barcelona’s historic Jewish quarter, in San Domenech del Call Street. It was built in the 14th century and is still standing today. It is the oldest structure in the old city core. The renovation and reconstruction carried out by architects Lapeña and Torres has ensured its vitality into the 21st century. 

The building occupies a corner formed by two narrow streets with the two fronts both spanning about 8 metres. The representative stone façade facing San Domenech del Call is characteristic for its entrance portal and hallway on the ground level, the triforia on the first floor and biforia on the second floor. The street façades and their opposite walls are about the same length and close to make a square floor plan. The floor plan is divided into three areas by interior longitudinal and transversal load-bearing walls: a patio in the innermost corner of the floor plan, a dominant area (space) between the patio and the representative façade, and the subordinated area between the large façade and the patio.