St. Louis has some great public art. The Gateway Arch is wonderful. The new Fernando Botero sculpture in Clayton is fabulous, cheeky fun. And who doesn't love to picnic next to Richard Serra's Twain downtown? But this year we salute the mysterious rock sculpture popularly dubbed the Shrewsbury Stonehenge. Much like the original Stonehenge, which we hear is somewhere in England, no one knows who made this sculpture, what purpose it was meant to serve or even when it came into being. But early in the summer, motorists began noticing, and then asking questions about, the carefully stacked structure of stones that sits on a rocky outcropping at the Shrewsbury exit off westbound Interstate 44. The site -- an inaccessible strip of no-man's land sandwiched between the railroad tracks and the interstate --raises the question: How'd the sculpture get there? It's not just an accidental pile of rocks, but a shrewdly designed form possessing a reverential, yet eerie beauty. It seems to change shape as you round the exit's curve, mocking your attempts to make sense of it. Some SoCo residents call it Ol' Stoney, but they don't much want to talk about it. Shrewsbury police and city officials claim to know nothing about it. Calls to the Missouri Department of Transportation and the federal government went unreturned. Do they have something to hide?