Peristyle House with the Dionysus Mosaic

Oriented north–south and close to the Rhine, this is one of the few houses of Colonia Claudia Ara Agrippinensium whose layout is largely known. More than 20 rooms, reached via a colonnaded hall, were arranged around a central garden—the peristyle—with a fountain, while storerooms or shops lined the street front. The building went through several phases: after its Claudian origins came a second phase around 80 AD under the Flavians, followed by a complete redesign around 230 AD. Some rooms had hypocaust heating, though only scant traces survive of other rooms' mosaics and wall paintings. About ten generations occupied the townhouse over some 300 years, until it burned down in a Frankish raid in December 355 AD.

On the night of 19 January 2007, storm Kyrill tore loose the wooden cover of the fountain on the cathedral square. Timber beams and planks weighing up to 70 kilograms skidded across Roncalliplatz, smashed through the museum's glass façade and fell onto the mosaic. Numerous tesserae came loose and several medallions were damaged, though the central image survived intact. Specialists from Luxembourg's National Museum and the Rhineland State Museum in Bonn assessed the damage, joined by restorer Christoph Merzenich of Erfurt University of Applied Sciences and two conservators from Rome's Istituto Superiore per la Conservazione ed il Restauro—the same institute that had helped recover the mosaic 50 years earlier. Tapping every tile revealed roughly 120 spots with loosened tesserae and abrasions up to three millimetres deep, adding up to a seven-figure repair bill. Visitors could watch the restoration, completed in July 2008, and its conclusion was marked with a Dionysus festival on 18 January 2009, the second anniversary of the storm.