The San Telmo Museum in San Sebastian Spain is home to the cities large collection of sculpture and paintings as well as their archaeological and cultural artefacts. Originally housed in the 16th century Dominican convent, the collection came to its current site in 1902, but by the mid 1990s it had already outgrown the space. In 2005 Nieto Sobejano Arquitectos won the competition for the expansion of the museum, and construction began shortly afterward. The almost unbuildable site, wedged between the old museum and the sharply rising mountain side, was used as inspiration for the shape and exterior appearance of the building. The 3,500 recycled cast-aluminum panels of the facade are designed to emulate the moss-covered sharp stone of the cliff behind the building while following the cities exterior boarder. Perforations in the panels allow for various types of plants to grow within them and also add to the various levels and layers of transparency of the building’s exterior. Only four different variations in panels were used in the cladding system, as the panels were rotated and flipped in order to create an almost infinite appearance in the hole pattern. The panels are attached back to a poured concrete wall system through a system of steel reinforcement. Through material choice and subtle change and layering, the San Telmo addition attempts to re-animate one of San Sebastian’s most significant historical sites.