TheADade-Collier Training and Transition Airport was originally planned as the Everglades Jetport, and construction started in 1968 on what was to be the world’s largest airport with six runways to support supersonic transport. Being surrounded by the Big Cypress National Preserve, environmental concerns halted construction, and when commercial supersonic transport didn’t arrive, the project was left as-is, now a lightly-used airport.A(© Google/USGS/DigitalGlobe)