For months, it's loomed over historic downtown Annapolis, battling the State House for dominance of the view.

The Coakley Williams construction crane marks the site of the future addition to the James Senate Office Building, a $24 million structure that will include a four-story rotunda topped by a Tiffany skylight and a three-tiered subterranean parking garage.

Officials say the construction, which started at the beginning of the summer, is about 30 percent done and remains on target for its Nov. 30 completion date.

"The shell of the building will be complete by late winter, early spring," said Vicki Fretwell, a spokeswoman for Senate President Thomas V. Mike Miller Jr. (D-Prince George's). "Then the task of filling out the interior begins."

Concrete has been poured for the walls and floors of the three underground levels, as well as much of the first floor. Steel supports anchor a single story, and work crews are preparing to put up the first-floor walls and ceiling.

Project manager Steven Reinert said the 80-person crew is set to begin constructing the upper floors in early March.

The crown jewel of the Senate addition, which is part of a three-year plan to renovate both the Senate and House office buildings, is the 20-foot diameter stained-glass dome that is currently atop the dimly lit Joint Hearing Room in the Legislative Services Building.

Not surprisingly, the dome--one of six pieces famed artist Louis Comfort Tiffany designed for the State House complex in the early 1900s--sees few visitors at its current home.

"Unfortunately [the dome] is in an interior surrounding," said Sen. Robert R. Neall (D-Anne Arundel), who came up with the idea of using the Tiffany dome as the skylight for the new rotunda. "It's not being shown, I don't think, in its proper context."

Before being moved late this summer, Waters Craftsmen Inc. of Huntly, Va., will refurbish any cracks and replace missing pieces of glass at a cost of about $100,000.

The piece was originally designed as a skylight for the old Court of Appeals building before being used in its current setting.

"It was beautiful," Neall said of the Tiffany dome in the court building. "It made the whole building. It's a treasure."