Boulder Creek is a day-use unit of Lake Cascade State Park, set on the Boulder Creek arm on the quieter west side of the lake about three miles south of Donnelly. It is the swimming and picnicking end of the park rather than a campground: there is no overnight camping here, and the whole place is laid out around spending an afternoon at the water.

Twelve picnic sites are scattered through a thick, mature stand of lodgepole pine, far enough apart that a group can spread out and close enough to the shore that you can carry a cooler down without a hike. From the sites it is a short walk to a genuinely good sand beach that the park designates and buoys off for swimming, one of three swim beaches at Lake Cascade. Two improved restrooms with flush toilets sit on site, which is not a given at an Idaho mountain reservoir and matters a great deal with small kids. Parking is split between a trailer and truck lot for boaters and separate car parking for the picnic area, so beach traffic and launch traffic stay out of each other's way. A fee station sits at the entrance.

The boat ramp here is one of six around the park and has two courtesy docks for loading and unloading. Check conditions before towing anything: Lake Cascade draws down through the season, and when the water gets low enough the park posts Boulder Creek as launch at your own risk. Canoes, kayaks and paddleboards are unbothered by that, and the Boulder Creek arm is a sheltered piece of water that stays manageable when wind has the main lake choppy.

Lake Cascade itself is a Bureau of Reclamation reservoir on the North Fork of the Payette River, held back by Cascade Dam since 1948 and sitting at about 4,828 feet. Idaho anglers know it as the state's jumbo yellow perch water, and it also holds rainbow trout, smallmouth bass and kokanee. The West Mountain range runs along the lake's western shore, and the last hour of light before sunset is the reason a lot of families stay put well past dinner.

Getting there: the unit is at 12742 Hereford Road, reached off Highway 55 between Donnelly and Cascade. Day-use hours are 7:00 a.m. to 10:00 p.m. Every motor vehicle entering the park pays a 7 dollar day-use fee or displays a valid Idaho State Parks Passport.