Ground was broken in Central Park yesterday on a multimillion-dollar restoration project that will transform the city’s oldest police precinct into one of its most advanced.

The castle-like structure New Yorkers pass while crossing the park on the 86th Street transverse is the 22nd Precinct House, built in 1871. The building will undergo a $45 million transformation that will bring it into the 21st century, Mayor Bloomberg said at a ceremony yesterday.

The remodeled precinct house, slated to open in 2010, will boast a huge state-of-the-art command center enclosed by a glass atrium. The entrance to the glass enclosure will be constructed in part with bulletproof glass, making it the first precinct house in the city with such a feature, a deputy commissioner of the city’s Office of Management and Budget, Daniel Diehl, said.

The U-shaped design of the renovation architect, Karlsberger, is based on the shape of the original precinct, which once served as a horse stable.

In order to distinguish which of the stone blocks from the original structure could be recycled into the restoration, the designers surveyed each one, the project manager for Karlsberger, Fred Basch, said. The results were then put into a database and analyzed, leading designers to establish that about 70% of the new precinct’s stonework would come from original stone blocks.

At the ground breaking, Mr. Bloomberg said Central Park is “the model for where European parks want to be,” and noted that it was fitting that police officers patrolling the park would be getting a comfortable new workplace.

In 1982, 700 robberies were committed in Central Park, a number that dropped to 26 last year, the mayor said.