Heidenlöcher, Castle ruin on Kirchberg, Deidesheim, Germany.

Heidenlöcher is the ruin of a refuge fort on the 344 m Kirchberg above Deidesheim, ringed by a collapsed dry-stone wall about 450 m long that enclosed some 1.3 hectares. Inside, roughly 80 to 85 single-storey pit houses of 10 to 20 m² each survive as wall traces, with one 80 m² hall standing out. Two gates pierced the wall, the northern one built as a zwinger.

The fortification was probably built in the 9th or 10th century as forced labour to shelter local inhabitants from Norman raids. Its original name is lost; the current one arose in the 18th century when the site was attributed to pagans. Friedrich Sprater of the Historical Museum of the Palatinate excavated in 1907/08 and thought it was a Celtic settlement. Later research showed the site is over a thousand years younger.

The name Heidenlöcher means "pagan holes": in the 18th century the site was attributed to heathens, and the second part refers to the hollows left by collapsed buildings. The first part of the name also reflects an early theory that the site was a Celtic settlement. The ruins are a protected cultural monument, so finds must be reported to the heritage authorities.

The ruins lie on the wooded summit of the Kirchberg, about 2.5 km northwest of Deidesheim; the late Gothic Michaelskapelle of 1470 stands 350 m to the east-southeast on the same hill. The ring wall, about 450 m long, encloses roughly 1.3 hectares, so allow time to walk the whole circuit. Excavation and the targeted collecting of finds require a permit, and chance finds must be reported to the monument authority.

The site held 80 to 85 single-storey buildings, mostly sunken-floor houses of 10 to 20 square metres with dry-stone walls of broken stone and boulders. Only one structure measured 80 square metres, and it probably served as a meeting place. No hearths or rubbish pits were found, so the fort may never have been permanently inhabited.