Global City: Singapore
Singapore is interesting for various reasons. First, it's a city state in Southeast Asia. Second, it is the most developed region in Southeast Asia. Third, it is a hub for travellers across Southeast Asia. Not being a Megacity, Singapore has clean air and streets. Traffic rules are (most of the time) followed and everything looks and feels neat. So even if you don't have any business in Singapore you mind end up spending a day or two there as part of an extended overlay between two connecting flights - voluntarily.