INSTRUCTIONS: Go on a walking journey and every fifteen feet draw a chalk arrow in the direction you're going. At the end of the trip, leave a big pile of chalk so a stranger can continue your journey.

OR

Walk a short route alone, then send a collaborator the last segment of your trip so that they can pick up where you left off. You may complete this in separate cities by using more generic instructions (e.g. walk three blocks, then turn left). Finally, walk the complete route you and your collaborators have created.