This is the fossil stem of a giant horsetail plant: *Calamites communis*. It dates back to the Carboniferous Period (359–299 million years ago). This object is part of the historical ‘Ettingshausen collection’, which is on permanent loan from the Institute of Biology, University of Graz. It is not currently on display. **Specimen**: Large, sand-filled stem of a fossil horsetail plant **Inventory number**: NHMW-GEO-2024/0188/10961 **Collection**: NHMW, Geology & Palaeontology Dept., Palaeobotany (curator: Chris Mays) **Origin**: Karviná coalfields, Czechian Silesia, Czechia Find out more about the NHM Vienna [here](http://nhm.at/en). Scanned and edited by A. Haider (NHMW) Scanner: Artec Space Spider Contribution to the digitization project „Einsichten in die gesellschaftspolitische Dimension des NHMW über die Jahrhunderte von der Prägung des Wissenschafts-Verständnisses bis zum Nationalpark in der Lobau“ funded by the [BMWKMS](https://www.bmwkms.gv.at/).