This is an extremely walkable area and a great time. Replete with boutique shops and a wide range of dining, this area has lots to offer. Pearl street is mostly blocked off to foot traffic so we recommend the best option as starting on one side of the street and wandering into whatever sparks your interest weather it be tea shops, coffeeshops, shopping, or a quick bite, this is where it happens in boulder. We have listed a few options below that are personal favorites
This is a chance to explore some of the unique and delicious breweries in the Boulder Area. Colorado boasts as the largest purveyor of microbreweries in the country and there is no shortage of fine venues here. While the taproom offers some fine choices, just look on google and you will find a menagerie reputable options nearby.
Boulder Reservoir/ Coot Lake Trailhead: 5.3-6 mile loop around the reservoir with the Flatirons in the background. https://www.alltrails.com/trail/us/colorado/boulder-reservoir-loop-trail
Flatter trail around Boulder
Foothills trails up outside of Boulder
There are plenty of museums around if that is your thing and you aren't looking to explore the great outdoors. Most notable is the Center for Atmospheric Research (interactive exhibits on how the weather is forecast), but not to be excluded are the the Fiske Planetarium, the Boulder Museum of Art, the Shelby American Collection, the University of Colorado Museum of Natural History, the Museum of Boulder, or just roaming around the University of Colorado Campus. This includes a link to a travel guide that explains these options in a little more detail.