The Designers' Open House at Cedar Knolls adds glitz to a Laurel Hollow mansion

What makes the Art Deco-inspired designer show house opening Saturday in Laurel Hollow even better is knowing what lies beneath the home's three sumptuously decorated floors.

A secret door in the powder room off the grand foyer of the circa 1930 Georgian-esque mansion leads downstairs to a space believed to have once been a speakeasy. Its remnants in the dark and cavernous basement would fascinate any historical house lover -- cobwebbed bottles of booze, a door in the floor that might have once led to a tunnel connecting the property to Cold Spring Harbor, a mysterious space plastered with vintage Alberto Vargas pinup girl prints, what looks to be a Prohibition-era safe room. Visitors will have to imagine what's downstairs and enjoy the thought -- the space is off limits for insurance reasons.

The underground details add to the period romance of Cedar Knolls, which gets a decorator touch as its owners try to snag a buyer for the home, priced at $2.495 million. Straddling what once was the Louis Comfort Tiffany Laurelton Hall estate and a property where John Lennon used to summer, Cedar Knolls was built for railroad magnate Jay Gould's grandson and was designed by the architectural firm that worked on the Whitney Museum of American Art's Greenwich Village site.

Many of the 26 decorators found inspiration in the Gold Coast era while designing the rooms. Here are some of the trends that emerged, straight up.

The walls in Baldwin designer Elizabeth Holmes' sitting room -- called "The September Issue" -- look like pressed tin. They're actually covered with high-end Phillip Jeffries wallpaper that is lacquered and embossed. "A definite trend in the industry is metal," she says.

You barely notice the seashells in Sea Cliff designer Rebecca Goodman's guest bedroom, titled "Inspired by the Sea." That was intentional. In drawing inspiration from the water view out of the second-story room, Goodman says she wanted to be subtle. So she placed the seashells in two vases on both sides of the bed -- under the nightstands. There is a sculpture of an anchor, but it's made of wood. Lamps depict sea urchins in silver. The large photograph on the wall depicts rope but is almost abstract.

The butler's pantry gets a futuristic look with Huntington Bay designer Mary Gray's treatment. Gray used square hockey-puck lights and strip lighting, some on a motion sensor, in the open cabinetry. "You can create design with lighting," she says.