When Dublin Civic Offices were built in the 1970s, sections of the Viking City Walls were discovered on the site; some of these were sealed into a double height basement room for 30 years. The project creates a sequence of modern conference rooms within this volume by decisive intervention: the medieval wall is extended on its original line by a corridor, a hollowed-out space whose external dimension matches that of the old wall- solid become void.The rest of the architecture is made as an undulating timber wall and ceiling , folded up to fill the double height space and offer a view of the old wall from a new public entrance.