Kuirau Park, on the western side of downtown Rotorua has plenty of parking and lots of free mudpools to look at! This public area is a nice place to picnic or wander during the day. When I was a kid there was a miniture railway that was a lot of fun. Sadly, it has now been removed. One of the intriguing things about Kuirau Park is that the ground it stands on is fairly thermally active. New mudpools and steam vents regularly open up!
Unfortunately, this place is not worth wandering around at night. In the past few years, muggings and petty crime have taken place here. I was saddened by the amount of rubbish that was in some of the pools when I was there last. Even in New Zealand these things happen.
It makes sense that if Rotoruas main attraction is its natural geothermal wonders, then to see the steam and geysers and bubbling mud at their best you are going to have to pay to enter one of the main geothermal areas. However, Kuirau Park is a reserve with a popular walkway meandering through it, and which saw a fairly big eruption take place as recently as January 2001. You can wander through this area and witness the earth bubbling away and doing its thing entirely free of charge.
Rocks, mud and steam were hurled into the air to a height of some 200 meters as the eruption took place, lasting about a quarter of an hour. You can still see cracks and fissures in the ground with hissing steam escaping and hear the 'plop plop plop' of boiling mudpools. This is low key geothermal activity by local standards, but is still definitely worth having a wander round, especially if you are on a budget and maybe can't stretch to the entrance fee to view some of the more impressive displays.
Nice geothermal area on the north east side of town. A well manicured green park with you occasional boiling caudron interspersed.
Great place for an evening stroll waiting for the sun to set and the Rotorua night life to begin. (This park has the distinct advantage of being FREE, unlike many of the geothermal areas around Rotorua...)