In the south of the Netherlands lies the limestone plateau of the Sint-Pietersberg. As early as the Middle Ages, people started using limestone as a building material. Underground mining resulted in an immense network of caves, its corridor walls preserving a huge living archive, left behind by block breakers, tourists, people in hiding, soldiers, and priests. Fossils of Sauria have been found, sieges have taken place, people have disappeared, and treasures have been stored (such as Rembrandt's Night Watch). Around 1960, Jan Spee started photographing these corridor walls, which he meticulously mapped and organised. Compiled by Sven Gerhardt (NL), this book gives an overview and provides context and cross-references to Spee’s images.