yes.
in san ignacio, you MUST do the caving tour of actun tunich mikal (cave of the holy sepulchre). this cave was explored by national geo a while back. it cost us 70.00 US for the day...a big splurge as we were on a budget but it was one of the highlights of a three month mexico/central america trip. our guide was one of the first to explore the cave and a mayan scholar; i believe his name was raol. ask around for him.
we enjoyed:
- a two hour 4x4 approach after heavy rains in a 1970 range rover with a cresent wrench for a gas pedal and a 14 year old driver. we were the only truck to get stuck and had to be pulled out by a newer 4-runner.
- a great jungle trek approach with several river-crossings, clutching vines and watching a few of the less co-ordinated members of our group get thoroughly terrified.
- the unique experience of plunging into a freezing pool of water and SWIMMING into the cave mouth for a feww hundred feet, in darkness.
- a kilometer or so of underground river tunnel with all the usual amazing cave features.
- a huge amphitheatre with thousands of ancient mayan pottery vessels calcified in dripping limestone.
- a small tomb with something i will not describe because it simply must be experienced first-hand.

thanks for the great advice!