Although I think it is entirely reasonable (and practical) to dress for comfort when travelling, I don't think this means one has to sacrifice any and all sense of style. Although toting around a decent sized camera is a pretty big giveaway that I'm a tourist, at least I won't perpetuate the stereotype too much with my attire (I hope). A strapless cotton dress and decent walking ankle boots make a perfectly appropriate option.
Get the look:
Dress from Sportmax, 2 years ago. Similar here.