Rifle Gap State Park and the reservoir are a delightful place to visit.
There are numerous vantage points to view the water and mountains by car, a cool trail that circles the water, and of course access to the reservoir for boats.
The water was beautiful and high, though I heard it was low for a while due to drought. Many people were fishing, so I assume it's a good spot for that though I didn't have any gear along.
Definitely worth the short drive from town.