There are six Chests throughout the Ant Cave, and the one just northeast/east of the entrance inside sometimes holds a Crystal Ring. Many Rogues camp out in the cave, traveling to the various chests to work on their Lockpicking and Removing Traps skills.
The Queen's Chamber is a common location for group hunts for newer players. However, many parties underestimate the dangers of the Queen and die quickly. The Queen Ant is not a creature to be taken too lightly.
A beautiful Map of Ant Hill was made by Ames in Player Art off of the main site. All of the six chests appear on the map, as well as the Queen Ant herself. The Forest Entrance listed in the map is the entrance to the Rat Cave. The full-sized map is located here.