The fort is well-preserved, even has cannons! It was used to protect the area from the pirates who came past regularly.
The museum at the centre is really interesting and has a great mural on the wall.
Free on sundays to mexican nationals - actually there was no-one there to collect.
Chacchoben Mayan ruins are only 7km off the highway travelling north from Bacalar.
There are 4 pyramids and a ballcourt, really interesting and we were the only visitors.
There were 2 howler monkeys playing in the trees above us as we visited.
There isn't a lot to see around this small village. In the center is the old Spanish fort with great views and a little museum. It does not cost much and is of interest.