the galeria arte urbana (GAU) is an outdoor street art gallery located on calcada da gloria, next to the upper station of the elevador da gloria. the six large walls are painted by different artists and get repainted every once in a while.
“The GAU – Urban Art Gallery – is now closer to everyone.
We went from 7 panels installed on Calçada da Glória | Largo da Oliveirinha, to walls and facades, to waste collection trucks and bottle banks that can be discovered throughout the entire city….” source
a bit further down the road even more street art can be found:
more about the galleria arte urbana: gau-lisboa.blogspot.com and galeriaurbana.com.pt (both only in portuguese)