Spanish architect Alberto Campo Baeza has concealed an office block with walls made entirely of glass behind a sandstone enclosure in the Spanish city of Zamora (+ slideshow).

The architect matched the stone of the site's perimeter walls exactly to the exterior of the neighbouring Romanesque cathedral, which is located in the west of the historic walled city.

Behind the screen walls, two irregularly shaped courtyards are positioned either side of the glass building that houses the advisory board for the autonomous region of Castilla y León.

The sheets of glass that make up the exterior of the two-storey building are joined by little more than structural silicone. "It's as if the walls are entirely made of air," said Campo Baeza.

Glass fins separate the outer glass skin from an inner glass wall in front of the floor plates, creating a void that mimics the proportions of a solid wall.

This cavity is ventilated to keep the building cool during the summer, preventing a greenhouse effect.

The project was completed in collaboration with architects Pablo Fernández Lorenzo, Pablo Redondo Díez, Alfonso González Gaisán and Francisco Blanco Velasco.

Other impressive buildings we've featured from Spain include an extension to a historic town hall and a civic and cultural centre inside a former prison.

See more architecture in Spain »

Photography is by Javier Callejas Sevilla.

Above: aerial view of Zamora

Ground floor plan - click above for larger image

First floor plan - click above for larger image

Second floor plan - click above for larger image

Section - click above for larger image

Site plan and site elevation - click above for larger image