TAMPA — Senior U.S. District Judge William J. Castagna didn't want to leave his grand courtroom at the old courthouse until he had to, until the General Services Administration essentially evicted him.That was more than 15 years ago, when Tampa's historic federal courthouse seemed to be losing a battle to old age and seeping water and creeping mildew and limited budgets and limited imagination.On Wednesday, Castagna returned to see what his beloved old courthouse has become: a high-end Le Méridien hotel. And Castagna's old courtroom, the one with the leather-covered doors, heavy blue-velvet drapes and the ceilings approaching 20 feet high, had been turned into a ballroom."What do you think, judge?" asked Mayor Bob Buckhorn, a guide for a judges' preview of the new 130-room hotel, which opens Monday."Magnificent," Castagna said, looking for the big bas-relief American eagle, covered in gold leaf, that had been mounted above his bench. It was still there. "That eagle," he said, "when I got here, was a little bit tarnished, from years of I guess maybe they were smoking in here."Downstairs, Castagna's judicial bench had been cut down and installed on the ground floor for hotel staff."I'm glad that it still has some practical use," he said.That's the nature of the 16-month transformation, which cost $26 million. Every old system — mechanical, plumbing and electrical — was replaced. Every old space was repurposed.Someone asked: What did you do with the courthouse vault?"The vault is gone," said Gary Prosterman, the owner and principal of Development Services Group, or DSG, of Memphis, the lead company in the development team. "It's a guest room. The jail cells are guest rooms. We really used every square inch of the building, and we really needed to."Finished in 1905, the building has a beaux-arts design and neoclassical elements, like the three-story Corinthian columns at the front door.Federal officials closed it 16 years ago and gave it to the city five years later.For years, the city could do little more with the empty courthouse than spend $100,000 a year running the air conditioning in a fight against mold.But in 2011, after several unsuccessful tries to find a tenant, the city sought bids from developers willing to turn the courthouse into a high-end hotel. Some of the five bidders wanted city money, but not DSG.Not only that, but it had done 25 similar projects in 16 cities. Its work converting an old YMCA into a four-star hotel in Philadelphia won the 2010 Pennsylvania Historic Preservation Award for Adaptive Reuse.It was the perfect match, said historic preservationist Stephanie Ferrell, who made the initial contact with Prosterman and pitched him on the virtues of the old courthouse many times."It's finally happening," she said. "A lot of us could see it, but it takes people like Gary and the mayor to make it happen."On Wednesday, judges remembered the cozy community of the old courthouse, the characters who worked there and the place across the street where they could run out for Cuban coffee.But they also appreciated what it had become."It's wonderful what they've done," said U.S. Magistrate Judge Elizabeth Jenkins, standing in her old courtroom, now a guest room with a king-sized bed and windows looking onto N Florida Avenue and E Zack Street. "It's been very lonely to drive by and see it all shut up."Castagna, who presided over criminal trials and sent people to prison in his old courtroom, was glad that it would have a new life hosting wedding receptions and celebrations."All happy things, I hope," he said. "That's a delightful transition."Because before, he said, "there were not many smiles in this room."