Eighteen stories above 42nd Street, three Roman gods have taken a $21 million shower that cleaned decades of soot and grime from the western and southern facades of Grand Central Terminal.

The Roman messenger god, Mercury, is patron deity of the Metropolitan Transportation Authority, which runs the building through a subsidiary, Metro-North Railroad. A crack in his knee, like so many fissures in the building’s exterior, has been expertly repaired.

Hercules once again gleams white, the original color of the limestone shipped on the rails owned by the building’s benefactor, Cornelius Vanderbilt.

All that’s missing is the tip of Minerva’s pen. The goddess of wisdom awaits repair. For now, that figure is covered in duct tape to protect it from the elements.

The restoration of Grand Central Terminal, which began more than a decade ago with the $250 million reclamation of its neglected interior, enters its final phase in August, when stonemasons complete the southern and western faces, a $21 million project, and begin work to repair the many cracks on the eastern facade. Restoration is unnecessary for the northern side, which abuts the Met Life building.

By August 2006, when the $6 million restoration of the eastern facade is finished, Wayne Ehmann expects to have completed a decades-long endeavor. As chief architect for Metro-North Railroad, he has had the restoration of Grand Central as a continuing project since he came to the agency in 1984, when the vaulted ceiling in the main concourse was shrouded in dirt, and the lower level – where restaurants serve breakfast to more than 10,000 people each weekday – was vacant.

When the restoration of the outside of the building began in 2003, engineers and architects discovered the three statues of the Roman gods had fared better than the rest of the facade.

The foreman for the construction company in charge of the restorations, Kafka Construction, attributes that to the high quality of the Indiana limestone and the advantage Vanderbilt had in selecting it. Since he owned the railroad, shipping costs were not a factor.

“As the blocks got closer to New York City, they got more selective,” the foreman, Patrick Mahon, said. “If they didn’t like the stone, they just pushed it off the train.”

At the terminal, however, years of trains rumbling below ground created hundreds of stress fractures throughout the building’s exterior.

“The thing we found out was it was in a lot worse condition than we expected,” Mr. Ehmann told The New York Sun. “We found a lot of open joints and problems we couldn’t see when we started.”

Although the copper roof was replaced in 1984, as soon as restoration work commenced the building mysteriously leaked. Workers discovered that the water used to clean the building began leaking into the retail stores and offices in the terminal from the many hidden cracks in the facade. “Once water starts coming it’s almost impossible to see where it’s going to land,” Mr. Ehmann said. Stonemasons repaired the cracks using just the right mixture of cement, mortar, and sand to meet the standards of preservationists overseeing the restoration of the historic landmark.

“We got it right on the second try,” Mr. Mahon, said.

To accommodate the building’s need to absorb vibrations, Mr. Mahon said stonemasons intentionally created cracks or joints, and filled them with lead and caulking to allow the building to expand and contract. “This kind of gives the building a little flex,” Mr. Mahon said.

Now that the exterior restoration nears completion, Mr. Ehmann, who is 62, jokes about his next project: retirement.

“It feels good to have completed the whole thing,” he said. “It’s been fun the whole way.”