Mapnificent, a "Dynamic Public Transportation Travel Time Maps" tracker combines mass transit trip data for cities in its database with maps of those cities, and predicts how far you can get from a point of your choosing in the length of time of your choosing. So, we picked a starting point, and gave ourselves 30 minutes to get somewhere.
Say you're smack in the center of Downtown Miami. Not just the center, but at the Metrorail station itself, and you've got 30 minutes to get somewhere - anywhere - interesting. Well, you can go to Little Havana, Brickell, and Coconut Grove, but Coral Gables is a bit too far without automotive help. You'll reach Miami Beach, but getting to the actual ocean may be just a liiiiiitle bit of a stretch. Midtown and the Design District are in your grasp, but the leafy lanes of Miami Shores or anywhere further most certainly are not. Wanna get to the airport? No dice, that is at least until the Metrorail airport extension opens this summer.