A must-do in Rotorua, though be prepared to take the city's distinct smell back with you after the Sulphur Spa! The view from the pool was well worth it though! The Mud Bath, which the staff recommended us to do first to open up our pores, was such a unique and fun experience too! The mud was sticky-smooth, kind of like butter, and took to our body easily. Staff were attentive enough to remind us that after 20 minutes pigging out in the mud, it was time to leave the mud bath for health reasons. No time limit on the sulphur pools though I'm sure you don't want too long of a hot dip.
Before we entered the baths, we were given a health and safety talk, and a container to store all our belongings (change of cloths, etc.). The unlockable containers are kept at a manned booth, though on that day we noticed there were times when the booth was left unattended. So, we recommend not leaving any valuables if possible.
Gender-specific changing and shower facilities were clean and helpful in getting the initial sulphur stench off, though like I said, the stink sticks with you... For days.