In this spot you'll meet the three gorgon queens: Sstheno, Medusa and Euryale. They won't be happy to see you. If you approach the trio head-on, then you'll probably have to fight all three at once, but if you circle around to the east, then you can draw them to you one at a time. Just approach the gorgons slowly, and retreat when one notices you. Don't try and use a ranged attack to draw them to you. That will probably alert all three.
The gorgon queens are spellcasters, and Medusa can turn you to stone with her gaze. Fortunately, being petrified isn't permanent, and so as long as you fight the gorgons one at a time, you should be able to defeat them relatively easily. If you have to fight more than one at once, then be ready to quaff a lot of potions.
You won't receive anything for killing the three gorgon queens, but their deaths will update the quest "The Source of the Monsters," and it will cause the nearby petrified woman (#3) to wake up.