The Horreum, at the heart of the modern city, consists of underground galleries built in the 1st century BC, 5 meters below ground. They must have formed the foundations of a building, probably a market or warehouse (horreum meaning "storehouse"). Built above ground, the building was located south of the forum, on the edge of the cardo (north-south axis) of the Roman town of Narbo Martius. These underground galleries have survived the centuries, with various alterations and partial re-use as private cellars. Officially listed in 1838, they were classified as Historic Monuments in 1961, then developed and opened to the public in 1976. Along with the archaeological remains of the Clos de la Lombarde site, the Horreum is one of the only Roman monuments visible and open to visitors in the center of Narbonne. Together with the Narbo Via Museum and Amphoralis, it is part of the Etablissement Public de Coopération Culturelle (EPCC) Narbo Via, thus restoring Narbonne's prestigious Roman past.