Porto is a city well worth a sustained visit, but if you are walking through, I'd suggest that you at least take a rest day here. Porto has beautiful "bones", layered over by years of inadequate funds to maintain its beauty, and the result is a kind of gritty beauty that leaves most of us in awe.
http://www.nytimes.com/interactive/...urs-in-porto-portugal.html?smid=fb-share&_r=0
http://www.nytimes.com/interactive/...urs-in-porto-portugal.html?smid=fb-share&_r=0