In Waitomo, there are a number of tour options, including:
The Glowworm, Ruakuri and Aranui caves. You can get tickets to visit one, two or all three.
Lost World tour (4 or 7 hours). Extensive, adventurous tour including abseiling deep into the cave system.
There are various other options, including black-water rafting. Get in touch for details.
There are also some nice scenic walks in the vicinity:
The Ruakuri bushwalk leads through the Ruakuri Scenic Reserve, 3.5km from Waitomo Village near Aranui and Ruakuri Caves.
If you are okay to do more driving, you may also want to drive further west (35 mins) to Marokopa Falls, or even further to the black sand of Marokopa Beach.