Five high-rises, two of which would be 23 stories, have been proposed to replace the Putt-Putt miniature golf course and a garden apartment complex on one of the few remaining parcels to be redeveloped in what is emerging as Arlington County's new downtown.

The $100 million office and residential complex is to be developed by the Rockville-based Radnor/Buchanan Co., a subsidiary of the Sun Oil Co., on five acres in Ballston.

The firm last week submitted preliminary plans that call for two 23-story residential buildings with a total of 447 units, two 11-story office buildings, and a nine-story building that may be offices or a 315-unit hotel. There would be 1,732 underground parking spaces.

The project, to be known as the Ellipse at Ballston, features curving buildings surrounding an outdoor plaza. It was designed by the Arthur Cotton Moore Associates architectural firm, which designed Washington Harbour on the Georgetown waterfront and renovated the Old Post Office on Pennsylvania Avenue in the District.

"It's different from anything we've seen in Ballston," said Bob Brosnan, a county planner. "The architecture is different, a little bit more like post-modern architecture. It's also got curved buildings rather than the traditional square buildings we've seen in Ballston thus far."

The property -- across from the Ballston Common shopping center, which is scheduled to open Oct. 22 -- is bounded by Wilson Boulevard, Fairfax Drive, North Taylor Street and the Sovran bank on Glebe Road. Two corner parcels on Taylor Street that are occupied by a small shopping center and a bank were not sold to the developer.

The property is in a special zoning district that the county created for the Ballston core area that requires at least 50 percent of the floor space to be set aside for residential development. In exchange, developers are allowed extra heights and densities that are determined by a complex sliding-scale formula.

The Radnor/Buchanan project is under the maximum heights and densities the county allows in the district. The development is expected to win County Board approval, possibly this fall. Company officials hope to start construction in about a year; the work is expected to last a few years.

Arthur Cotton Moore said yesterday that "the main thing, the important thing about the project is its hole in the center -- an elliptical plaza which we hope will be the performing space for outdoor performing arts . . . . What these five buildings do is basically define and shape this major plaza for Arlington."

Thomas C. Parker, director of the county's economic development division, praised the developer's plans for open space, an outdoor theater and community meeting rooms.

With those features, he said, "The project begins to round out the central area of development and brings in a number of community uses which will add significantly to the 24-hour life we've been looking for in the Ballston area."

Robert E. Buchanan, local partner for the Radnor Corp., said yesterday that he has been talking to the Arlington Arts Council about gallery space. "We think it would be a nice asset for the project and for the county to have a presence in Ballston in one of the newer buildings."

Buchanan said he hopes that the outdoor plaza and stage area "will be a people generator and create interest in the center."

L.J. Bruton, owner of the Putt-Putt course, said he had expected the development. "I've been here a long time, but I guess I've been here long enough. I'm sort of looking forward to going home," said Bruton, who has owned the course for 26 years.

Jim Rank, who lives in Glebe Court apartments, said the residents had been notified to move by Sept. 15. "The courtyard here is gorgeous. There's trees in here that are over 50 years old. Why do they want to tear this down? . . . I've seen what they're doing across the street, and I don't care for it." Buchanan said that the remaining 60 tenants of the 77-unit Glebe Court apartments are people who have been on month-to-month leases for several years and that the company has been working with county agencies to help relocate the tenants.