As shown in the POTD from two days ago, religious icons in Lisbon seem to be off-limits as targets for graffiti. The same protection does not appear to apply to artwork in general as shown here. This was one of a set of photographs from India by a well-known Portuguese photographer which were decorating different areas of a square in downtown Lisbon. Or maybe they only target photographic art as I don’t recall seeing graffiti on any of the many historical statues we saw around town.
(We are back from Lisbon, but given the number of photographs I took while there the POTD subjects will continue to be from there for some time to come.)