Hic Mores Hominum Castigantur. ‘Here the deeds of men shall be punished’: this was the Latin inscription on the tympanum of the main facade of Lisbon’s Thalia Theater, once a genteel building raised by a Portuguese aristocrat and, since a fire destroyed it in 1862, an evocative ruin. It has now been turned into a venue for exhibitions, concerts and other cultural events by the workings of a triple intervention. First, the restoration of the theater’s old facade, with its elegant neoclassical porch. Second, the consolidation of the ruins of the stage area, now protected by a large bold shell of reinforced concrete dyed a terracotta color and recalling the old theater with its simple geometry, creating a huge void that functions as a multipurpose space and is characterized by the atmosphere born of the contrast between the finish of the new materials and the time-worn textutres of the ruins. Third, the construction of two small pavilions for offices and services, aligned with the perimeter of the site, opening on to the street through a skin of glass and creating a courtyard at the rear that serves both as an inner square and a filter against the hustle and bustle of the city.