Set of for Niska Banja hoping for a dip in the thermal waters.  Nice location in the hills.  After doing a bit of research it appears the waters have a high Radon content due to a bedrock of travertine.  I guess the spa's name "Radon" should have given us a clue.  No massages available either so we set off to the picturesque Sicava gorge, through 13 tunnels.  Meandered around trying to find a stopping place and ended up on an ever narrowing lane, sustaining multiple scratches by low trees.  Paused for a cuppa then decided to call it a day in this area due lack of riverside stops.  Drove on an hour to Sokobanja.  The spa was a bit grotty (unlike the photos) and the pools too deep to stand in which was uncomfortable however we had a cheap massage which made up for it a bit.  Walked into town for a meal of a delicious bigos style dish and decided to stay at the spa car park for the night.