This weekend, the Merill Oyster Racing Series returns to Denver.

Billed as the Ultimate Urban Adventure Race, teams are given a series of clues and using their smarts (and the smarts of their friends, who they can phone) they must search around town to find clues and complete challenges.

Some events in the past have seen competitors swimming in the tanks at the Denver Aquarium, riding roller coasters, or paddling the Platte.

While it’s probably too late to sign up, it should be a fun event to take part in next year, or you can donate to a team to support them. The money goes to the Make a Wish Foundation.