One of the main attractions of Rotorua is the hot pools and geysers. There is also that slightly sulphur smell. I have been there so often I hardly notice.
These photos were taken at a public park. It is unwise to go off the set path near any hot pool or thermal area because what happens next is unpredictable and dangerous.
However, if you think of coming to New Zealand, Rotorua is a must see and also the Thermal hot springs, and Thermal parks. You are safe if you follow the path and keep your eyes open.
There are many things to see and do in Rotorua.
The thumbnail is a thermal pool with mainly boiling water from a thermal spring from a public park. Note, there are gates around these areas for a very good reason,
There are also chemicals that come with thermal activity in the water. I think one element is sulphur or sulphuric acid or both. There may be other chemicals.