An incomplete European map is available at https://www.eea.europa.eu/data-and-maps/figures/european-indoor-radon-map-december-2011 https://www.eea.europa.eu/dat

An incomplete European map is available at https://www.eea.europa.eu/data-and-maps/figures/european-indoor-radon-map-december-2011 https://www.eea.europa.eu/data-and-maps/figures/european-ind... No data on Slovakia but given its neighbors situation definitely worth checking.