That's a good point. And it's really impressive how far you can walk without being exposed to the sky in central Boston or Singapore (or, I've heard, in Montréal).
Or the MIT campus with its tunnels (you can walk from building 1 to E19 without going outside, which I will probably do when visiting in January to avoid the cold weather).
Or the MIT campus with its tunnels (you can walk from building 1 to E19 without going outside, which I will probably do when visiting in January to avoid the cold weather).
https://whereis.mit.edu/