When Murray Maurstad and Vicki Aune were house-hunting in 1993, they fell in love with a unique flat-roofed dwelling on Lake Minnetonka. They had no idea that the house was designed by two prominent architects for a well-known environmentalist.

But they appreciated the 1966-built home's ahead-of-its-time features, including an open floor plan, simple geometric lines and expanses of glass that let in abundant natural light. Unlike many homes of its era, it was designed to have a strong connection to the land and to the water that surrounds it. In fact, the multilevel home sits only 10 feet from the sandy shoreline of Lake Minnetonka.

"Every single window looked out at the lake," said Aune. The couple bought the house because the lake setting was a good fit for their 12-year-old daughter, who loved water sports. "It was perfect for us," said Maurstad. "And we loved the architecture and design."

The unique design was the work of local architects Elizabeth and Winston Close, and the home's original owner was Dick Gray, who co-founded the Freshwater Society in nearby Navarre.

Before the closing, Aune and Maurstad went out to dinner with Gray and discovered that it was his basement laboratory, filled with test tubes and jars of fish and water samples, that they had seen when touring the home. Gray also was the mastermind behind Gray Freshwater Biological Institute, a state-of-the-art research lab, which was used by the University of Minnesota.

"We were amazed at his accomplishments," said Aune. "He had a mini-freshwater society in the basement of the house."

Gray shared photos and the history of the dwelling, which originally was a multilevel boathouse with a large lakeside deck. He had hired the Closes to design the extended Gray family's summer getaway on Lake Minnetonka in 1961. The main floor housed a living room, kitchen, dinette and bathroom. The unfinished concrete lower level was used for storing the boats during winter.

In 1965, a tornado destroyed everything but the block foundation and external concrete block walls. So Gray enlisted the Closes again, this time to design a larger year-round house using the existing walls and foundation.

The land the house sits on is known as "The Pass," a low point between two bodies of water — West Upper Lake and Halsted Bay — and was a favorite sandy swimming spot for Mound residents, said Maurstad. The couple became friends with Gray, who died last March at age 95 after five decades of environmental study, writing and activism.

After moving in, Maurstad and Aune chose to preserve the midcentury architectural charm as much as possible, because "Dick was proud of the house designed by Elizabeth Close," said Maurstad. "She designed the perfect midcentury modern house for this property."

Maurstad and Aune did undertake two major modifications: knocking down the dining room wall to open up the view of the lake, and updating the kitchen. Aune picked a mod oval-shaped center island big enough to seat 12, and crisp white cabinets to contrast against black laminate countertops. Appliances are hidden behind white panels, so "it doesn't look like a kitchen," she said.

Most of the original 1960s features are intact, from the den's redwood-paneled walls to the living room's retro pendant lights and floating slate hearth beneath the fireplace.

Two redwood decks wrap around three sides of the house, offering a view of sunrises and sunsets, as well as wildlife, including large white swans, said Maurstad.

The couple are still delighted by some of the home's frozen-in-time features. "We ring the old dinner bell on Saturdays when the Al and Alma's [tour] boat cruises by. Then we hear cheering," said Aune.

The couple's final project was transforming the lower-level walkout boat storage area into a teen-oriented game room outfitted with vintage pinball machines and jukebox, pool table, surround-sound theater and a bathroom. Maurstad converted Gray's old laboratory into his office.

After living in the home 21 years, Aune and Maurstad have decided to sell because their daughter now has a family of her own, and they can get their lake fix via their boat slip on the St. Croix River. The retired couple are considering a townhouse with less maintenance so they can do more traveling.

But when they find a buyer, Aune and Maurstad will be sad to leave the home's one-of-a-kind design, positioned a stone's throw from the lake shoreline.

"When visitors come for the first time, they say it feels like being on a ship," said Maurstad. "You can't see land — only water."

Other features:

• The multilevel home has 2,658 square feet and three bedrooms and three bathrooms.

• Original 1960s pendant lights in the living room and hallway.

• All new windows.

• Extensive landscape lighting highlights the home from the boulevard to the shoreline.

• Dick Gray was an avid tennis player and built a tennis court on the 0.75-acre property.

• Location, location, location: Less than a 30-minute drive to downtown Minneapolis, Wayzata, Excelsior and Lake Minnetonka Regional Park.

Gregg Larsen of Coldwell Banker Burnet has the listing, 612-719-4477.

Lynn Underwood • 612-673-7619