Barton Creek is the most-visited cave in Belize. It's a perfect introduction to the sport of caving, while harboring some impressive Mayan artifacts. Most people visit Barton Creek on a day trip from San Ignacio, which costs around $30, not including admission to the site ($10 per person). But if you have your own car, you can drive out to the site, pay a few bucks to rent a canoe, and tag along with an already scheduled trip. Just ask the guide; he'll be happy to pocket the extra dollars and show you around.
The trip is usually undergone in a canoe, unless the creek is high enough to float in a tube. High-powered spotlights are loaded into the canoe, and you practice rowing upstream to the cave entrance.
Once inside, you'll paddle for 30 minutes through impressive galleries of stalactites and past a genuine human skull placed by the Maya to scare off intruders.
At some point your guide will stop and haul the canoes up onto dry ground, and you'll continue into the cave on foot with headlamps to view ancient Mayan pottery and ceremonial artifacts.
If you're planning on visiting any other caves in Belize, like Actun Tunichil Muknal, or cave tubing on the Caves Branch River, visit Barton Creek FIRST, as it will be more exciting for you.
If you're not planning on doing any of the more extreme caving trips in Belize, do yourself the favor of vising Barton Creek. It'll be something you never forget.