Route: Barcelona Montserrat GR6 (Spain)

The route starts in Barcelona (Horta) and follows the GR6 and Cami de Santiago to get to the Monastir of Montserrat.

You can follow GR6 red/white marks (pay attention to variants and other GRs), you can find the original tracks online, or the yellow arrows for the Cami De Santiago. 
 

The route is nicer than one could expect, provided that it begins in a major city and it has to go through some towns and urban areas. I estimate 20% trails, 50% dirt roads, and 30% roads.

More info https://www.catalunya.com/gr-6-barcelona-montserrat-24-1-38?language=en