While I loved my experience at Hell's Gate, you don't have to pay or go far to see boiling mud and water in Rotorua. Just head on over to Kuirai Park: 

“Take a walk and discover the steaming, hissing and bubbling geothermal activity in this informal public park located right next to Rotoruas city centre.”

On the outside, the park doesn't look like anything special. So thanks @saggis for pointing it out to me! 

I was honestly mesmerized by all the steam and boiling geothermal activity!

I kept running from one steaming part of the park to the next like a little kid in a candy store!

The place felt like the Loch Ness monster was going to jump out and grab you at any moment!

And that's not far from the truth...

“In early Maori times the small lake in the park was much cooler and was known as Taokahu. Legend tells us that a beautiful young woman named Kuiarau was bathing in the waters when a taniwha (legendary creature) dragged her to his lair below the lake. The gods above were angered and made the lake boil so the Taniwha would be destroyed forever. From that time on, the bubbling lake and the steaming land around it have been known by the name of the lost woman, although the spelling has changed a little.”

The sounds coming from the earth only confirm the existence of the monster!

But of course, the park is not all eery! You can dip your feet into the hot foot baths located around the park. So nice!

Oh, and there are cool birds just walking around!

I didn't have time to go through the whole park - I was enjoying soaking my feet too much! And I'd love to go back for longer next time. Highly recommend it!