To preserve the excavated remains, they had to be kept at outdoor temperature and humidity while the works in the collections had to be kept within very strict curatorial limits. So great was the pressure for space that fragments of Gothic walls had to be incorporated into the perimeter, causing complicated structural issues. As with most of Zumthor’s buildings, the exterior reveals little. At ground level, it is pierced only twice, there is the glazed entrance to the foyer of the main building and the separate opening for the chapel.