Lory State Park is a short drive from old town Fort Collins and there are several hikes and a swimming access point to Horsetooth reservoir.
Enjoy boutique shops, restaurants, micro-breweries, and the charm of Fort Collins
The Poudre Canyon and River is a staple of Northern CO. You can tub (specific parts), fish, or just enjoy the river's beauty. It's about 20 minutes away from Old Town Fort Collins.
This massive reservoir is an awesome viewing spot, drive, and there are hikes nearby.