The Rio On River flows over rocks forming waterfalls and large pools. Atop a mountain in a far off area is the Mayan ruin called Caracol, which contains the tallest building in the entire country. I think this site is the most impressive and breathtaking ruin in Belize because it is a massive, basically unexcavated city hidden by the jungle. There are numerous living cave systems in Belize. Eroded limestone and acidic water form a biological soup causing caves and sink holes.
Underground rivers flow through caves that can sometimes be accessed by people.
These caves often harbor some exotic fauna. I had the privilege of participating in a six-hour tube float through the River of Caves. Three Mayan guides lead us through the pitch-black caves and we had only headlamps to light our way. We saw sunshine in a few spectacular openings in the cave revealing the dense canopy of the jungle. The earth in the caves is saturated and porous making it easy to have large active stalactites, stalagmites, and columns.