Altburg, Celtic fortress ruins in Bundenbach, Germany.

Altburg is a partially rebuilt Celtic hillfort on a roughly one-hectare plateau above the Hahnenbach valley near Bundenbach. Excavations by the Rheinisches Landesmuseum Trier in 1971–1974 reconstructed it in its 1st-century BC state, and since 1988 it has served as an open-air museum. The layout was traced from ditches and the holes of over 3,000 posts still visible in the soft slate rock.

The Treveri, a Celtic people, used this small hillfort in the 2nd and 1st centuries BC. The Rheinisches Landesmuseum Trier excavated the site from 1971 to 1974 and partly rebuilt it in its 1st-century BC state. The open-air museum opened in 1988.

Since 1988 the reconstructed settlement has served as an open-air museum, and each year on the third weekend of August the Altburg Festival fills it: the largest Irish folk festival in Rhineland-Palatinate, with international folk bands and a Celtic market. Sunday is family day with a large children's programme.

The open-air museum has been open to visitors since 1988, after the Rheinisches Landesmuseum Trier excavated the site from 1971 to 1974. The plateau covers about one hectare above the Hahnenbach valley; the former Herrenberg slate mine, now a show mine, and the Schmidtburg ruin on the opposite hill are within walking distance.

The foundations still trace the exact shape of the original houses today. This allows us to see how closely people lived together and how they used their space.