After finishing Upper Peak to Creek, you have the option to take Highway 86 to mid-station (top of the Creekside Gondola, base of the Big Red Express) or continue down Lower Peak to Creek to Creekside.
A whole 5.5 km top to bottom, this is a must do, as well as rewarding yourself with a beer at Dusty's in Creekside once the hard work is over! However, be sure to check the grooming boards throughout the mountain before committing to the whole run, as Lower Peak to Creek is groomed less often below Highway 86 than above.
If it has not been groomed all that recently the moguls will grow to a decent size and this run no longer becomes very intermediate-friendly terrain.
A quick look at the base of any of the chairlifts or within the Roundhouse will answer that question for you, and it is a fun leg-burning descent if you commit to the whole run!