The quartzite outcrops in the municipality of Sierck-les-Bains are spread over 10 hectares in the valley of the Montenach stream between the Sulzen mill and the Marienfloss chapel. The geological interest of the Taunus Quartzites lies in the very old age of this geological formation of eruptive rocks dating from the Devonian (primary era). The presence of a siliceous rock in a limestone area allows rare acidophilous plants to flourish. A discovery trail runs through the site. Four educational panels provide an understanding of the environments traversed.