Belize is on the smaller side of countries, but it's also on the lower side of population. It has miles upon miles of Rainforest, Jungle, Bush and (oddly enough)Pine Forests. It's got some beach too, but that's not nearly as much fun. If you set out into pretty much any of the foresty bits, you can see monkeys, toucans, parrots, jaguar, wild boar, scarlet macaques and the list goes on.
Mountain Pine Ridge is a pine forest in the middle of Belize, just outside of San Ignacio in the Cayo District of western Belize. Some of the highlights of the park include: Rio On Pools, Rio Frio Cave and Big Rock Falls. Some other things you can see and do in the area are Thousand Foot Falls, Twin Caves, and there are several other trails and caves that are accessible. Maximum Adventure Tours offers more that one way to see Mountain Pine Ridge. Aside from the regular Mountain Pine Ridge trip the Caving Tour goes there, the all-inclusive Cave & Camping Trip and the Caracol Tour.
If you have ever wanted to fly through the trees / canopy, hopping from platform to platform, on a small yet sturdy wire, with the jungle floor opening up below you; then this is your trip. In Belize, Maximum Adventure Tours takes you to Jaguar Paw on the Hummingbird Highway to engage in some of the best zip-lining in the country. The zip-lining course is at the same place as the Cave Tubing and the two can be combined (like Voltron) to make for an awesome day.
A lesser know zip-lining option is in Guatemala. On the way back from Tikal, there's a zip-lining course that you can stop at. If you want to hit that one after the Tikal Tour it's a few extra dollars and an extra hour.