Appearance:Dawn of Sorrow
Much like with Carmilla's Castle from CotM, Celia's castle isn't technically part of Castlevania, but is instead a seperate entity entirely. Of course, her castle was designed to look and function much like Dracula's, right down to the restored CV3 Grand Hallway.
While the structure of Celia's castle may be similar to Dracula's, many of the bosses featured in it are different. Puppet Master, Paranoia, and Gergoth come to mind as great examples of new and interesting Bosses made specifically for the game. Even bosses that have appeared before, like Balore and the Flying Armor, are given a different enough treatment to keep em interesting and fresh.
As we've established before, there are castles outside of Castlevania that compete for the tourism buisness of Romainia. Many of them were started during the reign of Dracula. One, however, was constructed after Castlevania Co. went bankrupt (which happened after Dracula's big defeat in 1999). Seeing a large hole in the tourism market, one of Dracula's board members, Celia, decided to take the ideas she felt worked best and make her own company.
Celia Tourism Inc. was born. It was designed to be the best of the new castles that sprang up after the demise of Castlevania Co. It featured the best of that old world, gothic horror charm mixed with modern aesthetics and design. The castle had everything, from a little Village reconstruction, to an Underground Waterway for the kids, to a full running Servants Quarters to meet all your needs. It even featured it's own, in house development company, The Abyss, which meant they didn't have to lisence out to the Chaos Realm Construction Co. for their additions.
Sadly, the tourist trade had taken a turn after Dracula went out of business, leaning far closer to the Vegas/Disney-Epcot style resorts. Old world charm just wasn't what tourists were looking for, and Celia's great venture was defeated (by business and by a hero named Soma).