Travel is mostly a structured excuse to pay attention. These five lean into that. A live grid of webcams pointed at New York’s worst lines. An Amsterdam canal house holding five-hundred-year-old occult manuscripts. An iPhone camera that quietly removes other tourists from the Trevi Fountain shot. A paper postcard with a hidden video of where you sent it from. And a disposable-camera app that makes you wait three days, three weeks, or a year to see the photo you just took.