The Devil's Causeway [Why are unique geological sights always attributed to the Devil?] in the Flat Tops Wilderness is a narrow rock ridge, roughly 50 ft long and about 4 ft wide at its narrowest. Although the hike is only 3 miles each way, the elevation change is over 1500 ft (10,300 to ~11,800 ft) and has steep switchbacks making this at least a moderate hike. This is one of the most popular hikes in northwestern Colorado with >5,000 people making the trek annually.
