Grand County's "summer activites" website says it all:
https://www.visitgrandcounty.com/play/summer-activities/
For some in depth hiking information:
https://www.visitgrandcounty.com/play/on-the-trail/hiking/
Rocky Mountain National Park Grand Lake Entrance
Trail Ridge Road, Grand Lake, CO 80447, (970) 586-1513
Hikes, vistas, scenic drives, wildlife, photo ops, camping ... there is literally something for everyone!