<p>Historical and recent records of slope failures in sandstones indicate that catastrophic rockfalls contribute to the widening of corridors and slots in orthogonally jointed rock, often posing a threat to local communities and visitors. We describe a rockfall that occurred during the night from 11 to 12th November 2021 in the Teplické skály rock city (NE Bohemia, Czech Republic). A sandstone pillar 10&#xa0;m high collapsed directly onto a tourist trail, destroying a wooden footbridge and producing huge amounts of blocks and debris. Using a field study, a detailed petrographic analysis, rock strength measurements, 3D modelling and animation and thermal imaging, we provide a detailed insight into this event, discussing the likely controls, triggers and mechanisms of failure. We demonstrate that the rockfall was controlled both by the original rock pillar morphology (a wider part standing upon a thin stem) and protracted chemical alteration of sandstone. The likely trigger, however, was the sudden drop of temperature on the days preceding the event, which resulted in frost expansion and a subsequent loss of internal stability of the sandstone body. Both field investigations and computer simulations provided evidence supporting hypothesis that the mechanism of failure was toppling, with the lowermost sandstone compartment acting as a pivot. Our investigation provides solid backgrounds to claim that long-term chemical weathering of quartzose sandstone not only contributes to a gradual, non-catastrophic disintegration of clifflines, but also to occasional rock slope collapses.</p>