Public domain
Underground tunnel system in Mount Saint Peter in Maastricht, possibly at the level of the Negendrup
From the collection of Rijksmuseum, Amsterdam. Free to download, adapt and use — no permission needed.
Credit lineOndergronds gangenstelsen in de Sint Pietersberg te Maastricht, mogelijk ter hoogte van de Negendrup. c. 1859. Alexander Schaepkens. Rijksmuseum, Amsterdam. Public domain.