Both courses are out-and-back. The lower 0.8mi is paved. The rest is dirt roads.

Both courses start on 23rd ave, just N of Colorado Blvd, over the river, by Courtney-Ryley-Cooper Park, in Idaho Springs.

• Go up two blocks, then turn left onto Virginia St.
• In ~1/4mi, go right up Virginia Canyon Rd. Here is where the climbing really begins.
• Go up Virginia Canyon Rd for 1/2mi, at ~9%, to the junction with Virginia Canyon (aka Oh My God, OMG) and Two Brothers roads.

5k: Go right onto the dirt OMG for ~3/4mi, at ~6%. Turn and return the same way.
https://www.mapmyrun.com/routes/view/4925858479/

10k: This was just the warm-up. From here it goes from steep to very steep, from paved to dirt.
https://www.mapmyrun.com/routes/view/4556729113

• Continue straight onto Two Brothers Rd. It’s a mile up a fairly consistent 12% to another junction with OMG and aid station.
• Continue straight up Two Brothers. The next mile or so has some stretches >15%.
• About 1/4mi before the top, the road curves right and flattens a bit.
• Just before the paved road, turn at the aid station and return the same way.

Two Brothers road is 2wd dirt. It’s steep and there are a few stretches where the gravel is loose, but the footing is pretty good overall. You don’t need shoes with an aggressive trail tread. Cushioning might be more important.