http://parcaventuregeneve.com/en/halloween-evenings-night-climbing-2017/

Not only will you be challenged by this tree climbing adventure, but it will be at night, with all the spooks and creepy-crawlies! They will supply you with a frontal headlamp. Costumes welcome. Limited numbers so make sure to reserve on their website as soon as possible. See photos of previous editions on the site too.