In the space of a few months, Rheda Brandt-Brager's penthouse apartment traveled from the early 19th to the early 21st century, without moving an inch.

Well, there was the odd inch here and there -- a ceiling raised, a floor covering simplified.

But, surprising as the transformation is from the former owner's formal, stylized Empire decor to a sleek, bright and witty contemporary look, even more surprising is that many elements in the old decor work equally well in the new.

Work on the apartment, in a 1920s high-rise in Guilford, was truly a labor of love for Ms. Brandt-Brager, a designer and gallery owner who moved to Baltimore from New York last fall and married local attorney Bernard Brager in March. It was a chance to use some cherished items from her previous residences and to incorporate some new pieces into a personal, comfortable home for her new life.

"We both knew we wanted it to be comfortable, but we didn't want it to be complicated," says Ms. Brandt-Brager, sitting on a ++ slightly '50s, slightly futuristic-looking, contemporary sofa by Angelo Donghia. "I didn't want Bernard to feel he couldn't sit on something. . . . We agreed that living in our new space should expand our comforts."

Knowing what you want is an important element in any decorating project, Ms. Brandt-Brager says. "A lot of people don't know what they like, or even what their favorite color is. I always start by asking, 'What is it about this room that dissatisfies you? What comfort is lacking?' Physical and visual comforts are very important."

The couple made few structural changes in the two-story space. They raised the dining room ceiling, removed faux-marble painted columns in the living room, and replaced all the floor treatments to give the spaces a lighter, more modern look.

But they kept the crystal and gilt-arrow light fixture and the brown marble tile floor in the foyer, the mirrored bulkheads in the living room, a Biedermeier-style, bow-front radiator cover in the dining room, the rich dark-wood kitchen cabinets and the black "ostrich skin" walls in the media room.

Today the apartment looks as if it might always have been this way, a unique blend of the sleek and the cozy. It's clear there was a guiding hand, but the apartment doesn't look stiff and "done." It is a textbook on how to bring personal style to a space that already has a distinct look of its own.

The foyer is an example. An imposing double-height space with a soaring spiral staircase, it previously had brown marble floors; faux brown marble trim; white, red and gold wallpaper in a pattern of draped fabric; and red carpet on the stairs, for a formal, classical look.

Ms. Brandt-Brager removed the carpet and the wallpaper. She painted the walls, baseboards and trim in the foyer white, and painted the staircase wall a light citrus green. The underside of the staircase is also painted citrus green. A Josef Hoffmann-design settee, three bare topiary frames, and three decorative balls Ms. Brager-Brandt coated in dried Spanish moss or lavender are the only furnishings. There were no structural changes, but the effect is bright and modern.

In furnishing the flat, Ms. Brandt-Brager says, "I brought a lot of things with me. I brought things from storage all over the place, in addition to my place in New York." What did Mr. Brager bring? "A suitcase," she says, with a laugh. "He is such a good sport," Ms. Brandt-Brager says. "He loves what has happened here."

Ms. Brandt-Brager, in contrast, has strong attachments to every piece she has acquired. "Most of the furniture is very strongly me," she says. "There isn't anything here I chose because I really needed it."

Instead, the pieces, such as the floor lamp bought at auction in Provincetown, Mass., five years ago, encrusted with Bakelite and other plastics from the '30s, or the spiral gold and black floor lamp by British artist Tom Dixon, or the faux-bamboo chair that was in her mother's house in Richmond, Va., are a study in personality. "Every piece is fairly distinct," Ms. Brandt-Brager says. "They weren't chosen to go together. Every time I've moved, it's a puzzle. It's like a little mini-collection."

Curiously, there is a lot of gold in her scheme, as there was in the previous owner's, with quite different results. Gilt objects and gilded touches on Empire furniture gave a luxurious, almost imperial, air to the previous owner's decor.

In Ms. Brandt-Brager's hands the gold is somehow eccentric and fun, perhaps because the largest gold objects are three screens by Egyptian-French architect Patrick Nagar. Each is a tall rectangle of gold-leafed paper, trimmed in black fabric and topped by elegant but whimsical poufs of pony hair. The screens can be moved around for different purposes and effects.

Another screen is the oversized white-paper fan tucked behind a silver, deco-style fire screen. "I had made little ones," she says, "so I decided to make a great big one. I think it's fun to play around with scale."

Artwork in the living room also exhibits this play of scale; one, a paper collage by New York artist Susan Anker beside the fireplace, is quite large; on the adjoining wall, divided by the door that leads to the foyer, are two tiny paintings.

Behind the creamy sofa is a "dreamlike" painting of a dog by Ms. Brandt-Brager's daughter Laura, 32, an artist. Daughter Susan, 29, is program director for an educational television channel, and daughter Vanessa, 25, is in her second year of veterinary school.

Ms. Brandt-Brager's love of contemporary design extends to her new gallery, called Grand Design, where she sells unusual and unique chairs, tables, chests, mirrors and other pieces by contemporary artists and crafts people. The shop, at 8 E. Franklin St., features works by artists such as Tom Dixon and Carolyn Quartermaine.

As for new things in the apartment, the dining room received two of the most dramatic new pieces. From Tom Dixon, the same artist who did the spiral gold lamp, she commissioned a table base made of white metal rods welded together in a shape vaguely reminiscent of Buckminster Fuller's geodesic dome, though this piece is angular, elongated and somehow animated. It's topped by a huge sheet of glass.

Above the table, however, is what may be the home's single most dramatic piece, a new chandelier by British artist Deborah Thomas. It's made of hundreds of pieces of shattered glass, wired to a frame and interspersed with tiny halogen lights. The shape is a flattened triangle with tufts of glass at intervals around the rim. It looks both frothy and dangerous at the same time. And how do you change the bulbs? "You have to know what you're doing," she says.

Knowing what you want, and what you are doing, of course, are the keys to getting a design look that's right for you. But Ms. Brandt-Brager suggests a third element, something that might be called the spirit of adventure. "We all live in the 20th century, not in the 18th. So how about a few contemporary pieces?" she says. "Most people do take their home seriously, they take their furniture very seriously. But I think it's good, when it's possible, to be light-hearted about some of the pieces one brings into the home."