I had the opportunity to spend a semester teaching at a university in Hong Kong several years ago which I really enjoyed, in part because Hong Kong is such a unique place in many ways.
I recently came across an interesting blog post, Hong Kong - City Without Ground, which describes one of the unique aspects of the city of Hong Kong - its 3-level landscape (ground-level, underground and overground). The introductory paragraph reads:
"If you’ve ever visited Hong Kong you will have undoubtably discovered that the city has three distinct, albeit tangled, levels - street level,underground and overground – which can be navigated by pedestrians via a complex network of elevated walkways and underground tunnels that have evolved over the past 50 years. You can literally walk for miles through interconnected shopping malls, office lobbies, train stations, parks and other public/private spaces."
The post also includes some 3D drawings of different areas of Hong Kong (from a new guidebook, Cities Without Ground) which give a great view of Hong Kong that's hard to envision in 1 or 2D.