It's like the Calder Valley Round on steroids.

A great event, highly recommended. The organisers let you swap between the long and short and options, so if you're feeling knackered as you drop down from Blackshaw Head, and don't fancy the climbs up Stoodley and in Cragg Vale, you can decide to jog back along the canal.
A word of warning: enter early. It's very popular and people are turned away on the day every year.