Decent sized reservoir, at the southern end below the water itself there is a small park with a large statue on horseback commemorating General Gang Gam-chan, a hero from the Great Battle of Guiju. It's possible to walk from here through the Forest Trail on the western shore - it looks like a very pretty walk of ~3.5km. If arriving on bike its lovely to park up on the high contain bank of the reservoir itself, maybe to have lunch if you are carrying food, if the weather is kind and to soak up the sun and view of this sizeable body of water.
There is a bike path on the eastern shore BUT take care since both directions are located on the left hand side of the road they have reversed the normal priority so the right hand lane travels with oncoming traffic. Should you be making a longer stop there are lots more cafes and restaurants beyond and north of the reservoir. It’s possible to cycle all the way up to the trailhead for Gwanggyo San, but it’s really not worth it unless you are going to spend somer time beyond the reservoir for a pit stop, since the road is barred to all vehicles including bicycles before it gets exciting gradient wise.