Eleanor Saitta: This is a really useful tool if you're trying to understand a place: http://budgetweb.com/travel-time-circle/

@dymaxion cool! Also a great way to see taxicab geometry in action (e.g. walking for 30 minutes in Salt Lake City). I tried making a similar project a few years ago to visualise how cities distort space-time, not as polished or useful as this one but showed individual tracks which is nice.