Go see the Myan ruins. The sight we went to had some amazing structures that you can climb! Although it feels some what disrespectful (like climbing on Stonehenge!) the views from the top of the 'pyramids' are breathtaking. Also, the trip to the ruins is magnificient in itself. We took a quick boat trip up a river then we trecked through a tropical forest to get there so there was the opportunity to see some of the local flora and fauna. Once there, it is a very easy hike, my grandfather was with us and he didn't have any trouble negotiating the path, but he was unable to climb to the tops of the ruins. The entire excursion was a wondeful experience.
When traveling to Belize, you must see at least one of the Mayan ruins and you must experience the barrier reef.
The ruins are an archealogical dig in progress. It was quite exciting.
The fish on the barrier reef are huge. We did some swimming with sharks and manta rays. the reef area has been protected and is not overun by tourists. The coral is quite unique-many different colors and types. We have not seen anything like it anywhere else in the world.