This narrow street is the main area for tapas in the city. The tapas here are the traditional, and also said to be the best ones in Zaragoza!
Wikipedia (Spanish) https://es.wikipedia.org/wiki/El_Tubo_%28Zaragoza%29
Facebook https://www.facebook.com/ElTubodeZaragoza
Address Centro Historico, 50011 Zaragoza, Spain
Coordinates 41°39'11.009" N -0°52'50.128" E