Bren Simon's mansion in the ultra-ritzy Bel Air neighborhood of Los Angeles is up for sale for $50 million.

The 20,000-square-foot estate went on the market in late February, about six months after the death of her husband, Melvin, the billionaire co-founder of Indianapolis-based Simon Property Group Inc.  

It's not clear whether the planned sale could become an issue in the legal battle over Melvin's estate launched in January by his daughter Deborah. If ownership was in Bren's name at the time of Melvin's death, or ownership was set up to revert to her at his death, the asset would be outside the estate. Attorneys for the parties declined to comment or did not respond to a request for comment.

It’s not clear how much of a profit Bren would pocket if the house fetches near the asking price. The couple bought it for $27.5 million four years ago, according to listing details. Since then, however, Bren, an interior designer, spent millions on upgrades.

The sale is creating a stir among residential real estate aficionados. Miami-based Haute Living magazine wrote that the opulent estate in Bel Air’s most prestigious area “oozes old-school glamour and eternal sophistication.”

Built in 2003, the property sits on 1.5 acres and offers a “breathtaking” view of the Bel Air Country Club golf course.

The home boasts eight bedrooms, 16 bathrooms and features a movie theater, indoor spa and gym, billiard room, wine cellar, poolside lounge, guest house, 2,000-square-foot master retreat and a subterranean garage to store a car collection.

The Bel Air mansion was not the Simons’ only expensive piece of property. Asherwood, a Carmel mansion with its own golf course, has an estimated value topping $50 million. Bren also has a condo in New York City, a home in Aspen, Colo., and other property.

Melvin married Bren, his second wife, in 1972.

In her lawsuit, Deborah is asking the court to throw out changes to Melvin’s estate plan he approved in February 2009, seven months before he died at age 82.

Deborah contends he was suffering from dementia and didn’t understand what he was doing when he signed off on the plan, which boosted the share of his fortune going directly to Bren from one-third to one-half.

The changes also wiped out a portion that was to go to Deborah and her siblings from Melvin’s first marriage—Cynthia Simon-Skjodt and David Simon, the CEO of Simon Property Group—and left charitable gifts stipulated in prior versions to Bren’s discretion.

Bren, 66, contends the changes reflected Melvin's wishes.