This rustic, off-grid treehouse overlooks the Bull Run River and its steep-sided canyon. Set 30 feet (9m) above ground, the eco-friendly design means the tree can still grow and the wooden house is gently hugging its trunk. There's no shower and the toilet is the composting kind, set a little away, but despite feeling on the edge on the world, Sandy, with its pubs and cafés, is just a 10-minute drive away.