Dear John: You recently joked that President Trump’s Mexico wall should be made of vinyl siding and have planters. That reminded me of something that happened a generation or more ago in NYC.

You will recall when vast sections of the South Bronx looked like Berlin in 1945 because of the plague of tenement fires which had depopulated whole neighborhoods.

The bombed-out skeletons of buildings were visible to tens of thousands of motorists every day on the Cross Bronx Expressway. They were an embarrassment to the city.

Then the city turned one precinct from “Fort Apache, The Bronx” into “Little House on the Prairie.” It installed posters in every open, glassless window that was visible from the highway. Every poster was identical, showing an open window with a flowerpot in it — making it look like the apartment units were still occupied by happy citizens when they were empty.

It seems to me Trump could do something similar on The Wall.

Dear J.N.: I don’t think I ever witnessed that scene firsthand, but I remember the days.

Maybe Trump can have silhouettes of fleeing people on the American side of the wall. And on the Mexican side there would be images of people heading toward America.

It could turn into quite an art project.