The intervention to enlarge the existing auditorium (built in the 1980s, under the brick walls of an ancient building) consist in an underground entrance foyer and some service rooms.

The entrance to the foyer is throught a square based glass pyramid, which introduces the public to a helicoidal staircase and a lift, both in glass, situated in the centre of the hall.

The ceiling of foyer (with an opening equal to the size of the base of the glass pyramid) is a square reinforced concrete slab, with a side of about 20 metres, which supports more than 2 metres of soil, as well as the glass pyramid. Said slab is supported by a reinforced concrete grid beams which remain inside the soil and with the same inclination as the glass pyramids.

SIO carried out the design and the supervision on-site of all structural works.

Of considerable importance is the structure of the pyramid proposed by SIO, totally in glass without steel profiles; steel has been used only in the connecting joints between the multilayers glass beams, which are the real skeleton of the pyramid, and in the link beetwen glass beams and glass panels.

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