Medieval monasteries commonly featured functional subterranean structures like drains, cellars, and crypts, which are often mistaken for 'tunnels' in modern folklore.

Monastic sites were complex, self-sufficient communities requiring sophisticated infrastructure. Drains were essential for waste removal and sanitation, often running beneath buildings and courtyards, sometimes stone-lined and large enough to be walked through for maintenance. Cellars and undercrofts provided cool, secure storage for food, drink, and other supplies, or formed robust foundations for multi-story buildings. Crypts, while less common in Cluniac priories focused on burials in ground-level cemeteries, were typically sacred spaces for relics or important burials. These functional, often substantial, subterranean passages and chambers can easily be misconstrued as 'secret tunnels' by an uninitiated observer, particularly after centuries of decay and the growth of local legends.