The rock is similar stone to Eldo, and not like the softer sandstone that is primarily in the area. There was a write up in Rock and Ice (Miniguide in Rock and Ice #89, December 1998, Cover photo is a guy ice climbing) that gives a good description. Lots of hard problems with a flat landing...
Getting There
It is right in the middle of Mathew Winters Park. The main trailhead is just south of I-70, and the Morrison exit. There is an easier way to get to the boulder than approaching from this trailhead, but, I wouldnt know how to describe it without getting somebody lost. So, to approach it from the main trailhead... Park at the West parking lot, and follow the trail into the valley. Where it splits, take the lower trail (take a left). After, I guess, about 1/2 mile or so of easy biking/running trail, you will see a big square boulder about 100 yards downhill on your left. It's pretty obvious when you get there.
The most obvious line on the boulder and probably the best! Start on two postive pocket and dyno left hand for a pocket. Top out up and left!!! ...[more]
pretty cool chunk of rock, and most of the stuff is indeed very difficult, although there are a few moderate problems on the right-hand side of the northern face with nice top-outs and good landings...should you fall.
The MB can also be reached by taking the main entrance into Red Rocks (i.e. Jewel/Alameda goes across C470, along Dinasaur Ridge, back down the other side, then into Red Rocks). Go about a mile up the road. When it turns South, a dirt parking lot will appear on the left. From here, one can cross the road and take the RR trail into Jeffco (Matthews/Winters). After a series of switchbacks along a beautiful red wall, a fork occurs. Either continue up and have a nice hike, or take the trail right, below the ridge. After about 1/2 mile you will see the MB downhill on the right. Keep going past it till you find the trail. Watch for cacti, snakes, slumbering elk, and prarie dog holes.