No those aren't the cave paintings of Lascaux. It's the BQE, specifically the retaining wall under the Brooklyn Heights Promenade. I was thinking this would make another good site for the homeless "Tilted Arc" sculpture. But time and traffic conspired to give me a closer look.
Who needs Serra and his Cor-Ten when we have flaking concrete?
And, a little further, on striated concrete? Perhaps the time has come for the great Werner Herzog BQE film.