Runners in Philadelphia say they're mystified by odd pictographs painted on streets throughout the city.
The symbols, always in white, consist of two circles and a mushroom-like icon loosely joined with a collection of angular shapes. Because the symbols appear directly in the narrow lanes favored by runners, many locals have speculated that they are some sort of message directed at them.
"It depends on how you look at it," said Thomas Yorke, 29, one such runner. "From one angle, it almost looks like a sort of face, with two eyes and a little puckered mouth and a really messed-up nose."
"But why would someone take the time to paint that on a public street?"
Others wonder whether the indecipherable glyphs are the work of a guerrilla artist.
"I heard Banksy is behind it," said Jon Greenwood, 44, another regular runner, referring to the anonymous street artist and activist based in the UK. "Which makes sense. To me, it's obviously a political statement. I mean, look at it."
For now, the provenance of the artwork remains a mystery. One recent afternoon a small group of runners stood around one such symbol as cyclists streamed around them, and no one knew quite what to make of the puzzle.
"Obviously this meant something to whoever painted it," said one. "But what?"