The two man-made islands sit in the middle of the Anacostia River, weed-filled refuges a stone's throw from Robert F. Kennedy Stadium. Once it was thought that Kingman and Heritage islands could serve as the city dump. Federal officials wanted to create a large recreation center, while D.C. officials sought to build a Bicentennial park.

All the ideas went for naught, however, the victims of congressional overseers who felt the ventures weren't worth a dime of the taxpayers' money.

But what was an eyesore to Congress is "mystical" and "enchanting" to Bina Sella di Monteluce, a wealthy, 35-year-old woman who helps manage her family's industrial, shipping and trading enterprises from her home in London.

Di Monteluce and her American representatives have now won the District government's support to create a 50-acre, $40 million entertainment park on the islands that will be roughly modeled after Tivoli Gardens, a collection of rides, amusements, stores and other attractions in the heart of Copenhagen.

If the development plans materialize, the scruffy islands, now known as National Children's Island, will be filled by the spring of 1987 with a mix of restaurants, shops, an amphitheater, modest-sized rides, educational and entertainment pavilions and a range of activities for both children and adults.

Di Monteluce said she has pledged $4 million in equity for the project and is committed to creating the park. In the meantime, the idea must still be formally approved by a variety of federal agencies, including the National Capital Planning Commission, the National Park Service and the Commission of Fine Arts, as well as the District government.

Even though final plans have yet to be drawn, "this is a project the District supports," Fred L. Greene, the District's planning director, told the planning commission this week.

Di Monteluce, who has development investments in Atlanta, Houston, Dallas and San Diego, said in a telephone interview that one of her financial advisers suggested the project to her in the spring of 1983, just after she found out that she was pregnant.

Linking the good news of her pregnancy with the idea for the park, di Monteluce, of Indian descent but described as being married to an Italian count, said, "I'm Indian. I'm very fatalistic. The idea really appealed to me. I just had to do it."

Last April, di Monteluce said she visited the islands and became convinced that the park should be built.

"It's mystical," she said of the site. "I think it makes an enchanting setting. I find it surprising that nothing's been done on it before."

Di Monteluce apparently is alone among investors in her enthusiasm for the site, which is three miles from the Mall's monuments and museums that attract most of Washington's tourists.

Nearly four years ago, the District government asked the board of the National Children's Island Inc., the nonprofit group established to seek a developer for the islands, to draft a new proposal that would be financed without public funds. But for one reason or another, the group was turned down by 10 firms that already have built amusement or theme parks throughout the country.

Nonetheless, di Monteluce remains undaunted about the financial risk in creating a theme park at a time when other firms have decided that such attractions are not the gold mine they once were believed to be.

"Ultimately, with anything in life," she said, "you never know what's around the corner."

But di Monteluce's firm, Island Development Corp., has performed some market research. One consultant predicted that 3.3 million people would come to the park annually and that 1,300 to 1,800 jobs would be created. Cambridge Seven Associates, the Massachusetts archi-tectural firm that designed the National Aquarium in Baltimore, was hired to draft plans for the Children's Island project.

"It will give Washington something else to do," di Monteluce said. "In Europe, people have always had places to meet. I don't really feel the site is out of the way. If we can offer people something, they'll come."