It’s important to stay hydrated while flying, but you’re better off BYOW (Bringing Your Own Water) rather than grabbing a free drink from the beverage cart. Tests done by the EPA a few years ago showed that one out of every seven planes had tank water that did not meet federal standards, and in fact contained bacteria like E. coli.

How often do we wander new territory, or even revisit places we’ve trod before, wishing we had a better sense of place we’re walking through, of its interesting backstories? After Groupon parted company with its co-founder Andrew Mason, Mason decided to liven up walking explorations throughout many of the world’s great cities with downloadable audio tours.