There is no longer a piece of the moon on Michigan Avenue.

The moon rock resided for years in a glass window next to the main entrance of Tribune Tower, a building adorned with famous stones from around the world.

Legend has it that when the Tribune’s magnificent new skyscraper was erected in 1925, powerful Chicago Tribune publisher Robert McCormick ordered his reporters around the globe to send him historic stones from the four corners of the Earth.

And being good "Tribune men," they did just that.

The tower is adorned with more than a hundred stones, from a chunk of Tom Sawyer’s Cave in Missouri, to a rock from the Custer Battlefield at the Little Bighorn in Montana, to a piece of Abraham Lincoln’s home in Springfield.

There's a stone from the White House, another from the Colosseum, a piece of rock from the spot where Washington crossed the Delaware, even a chip off the Taj Mahal. Inside, in a special case, is a stone purportedly removed from the grotto where Jesus was born in Bethlehem.

The most recent addition, a piece of twisted steel from the World Trade Center in New York.

But no more moon rock.

Tribune spokesman Gary Weitman said the display had become somewhat dated, and that company officials asked NASA if they might send a new rock which can actually be embedded in the building with the others.

The space agency agreed, but asked that the Tribune rock, which had been on loan for decades, be returned.

"We sent the moon rock back to them several weeks ago," Weitman said.

After the new rock arrives, plans are to encase it in a protective sheath of Lucite before it is embedded in the tower’s walls.

For now, visitors will have to marvel at chunks of the Mesa Verde cliff dwellings in Colorado, the Forbidden City in China, and Notre Dame Cathedral in Paris.

There is still a piece of rock from Craters of the Moon National Monument in Idaho. But for the real thing, you’ll have to wait.