I'm a firm believer in the black ballet flats, with a good extra insole if needed. When I'm travelling in Europe or Asia, I'm most interested in a) walking EVERYWHERE to get a good feel for a city and b) upscale shopping. The ballet flats are comfortable enough to handle 8 hours of exploring (try a few pairs to find the comfiest for your feet, then buy many, many pairs of them. I am a big fan of Paris-based Repetto), but they're also chic enough that you don't feel out of place walking into Selfridge's or Colette. And they work with casual and dressier outfits! It really does boil down to finding the perfect pair, though - I've had a few flats that have been unbearable and a few that have served me so well I've literally worn them to shreds. Do check out Repetto, though - they began life as a ballet slipper company and their shoes are dance-inspired, and feel like slippers you could run a marathon in.