In Poland, there are over 40 underground tourist routes, but radon concentrations are measured only in a few of them. The underground tourist routes, such as caves, old mines, building constructions under old towns and dungeons are the environments with potential radon concentrations that may exceed several thousand times the atmospheric concentrations. Among other routes, the following should be singled out: the drift of the former Kowary uranium mine, Niedzwiedzia Cave located near Kletno and close uranium mine in Kletno (the Sudetes). In the former, the mean annual radon concentration is of the order of 400 Bq m −3, and in the latter it reaches over 2000 Bq m −3. Measurements performed in 2004 in the closed uranium mine in Kletno showed that average radon concentration in that route is 1800 Bq m −3.