The core of the Aachen cathedral is the so-called palace chapel („Pfalzkapelle“). It has an octagonal central space which is surrounded by a sixteen-walled gallery. Attached to this ring are the westwork, the gothic choir, and a number of chapels which were built later. While the carcass of the core buildings was erected by Charlemagne 1200 years ago, the interior design dates from the 19th century. In the course of historism the former baroque design was regarded obsolete and replaced by a new interior. In this context the wall surfaces were covered with strongly textured marble and the arch was decorated with elaborate glass tessellations. During the last century most of the marble surfaces and tessellations got very dirty and partly loosened from their subsurfaces. An extensive restoration and cleaning procedure became inevitable. My photogrammetric pictures document the current state and form a basis for the survey and mapping necessary for the restoration process.