Fed by rainfall and snowmelt from the west, Boulder Creek runs straight through the center of town. A picturesque shady path runs alongside, and numerous swimming holes offer opportunities for a quick dip or inner tubing.
Boulder has nearly perfect weather, but a few summer days do get painfully hot. Happily the creek is always available, always cold, and taken advantage of by hundreds of locals young and old. Some of the best entry points are at Eben G. Fine park, under the pedestrian bridge behind the Millenium Hotel and just east of 28th street.
For a dash of adrenaline, look behind the Millenium Hotel where locals jump off of small retaining walls, or to the tube run at Eben G. Fine park.