It’s not the island of Lanai, but another major piece of Hawaii is for sale.

Some 600 acres, including about half of downtown Kailua, have been put on the market by the Harold K.L. Castle Foundation, one of Hawaii’s largest private landowners and charitable foundations.

The foundation’s asset-management arm, Kaneohe Ranch, retained brokerage firm Eastdil Secured to find a buyer or buyers for the property collection.

The offering is being made to select investors and is not being widely publicized, but a copy was obtained by the Star-Advertiser.

Eastdil touts the portfolio as a “once-in-a-lifetime opportunity” to own a “phenomenal” real estate collection that includes shopping centers; land leased to businesses; and the 38-acre town center of Kailua that includes land under Foodland, Safeway, Whole Foods, Times, Longs Drugs and Macy’s.

Other holdings of the foundation and its affiliates include the land under Kaimuki Shopping Center, Windward City Shopping Center and Pali Palms Plaza.

About 50 acres on the mainland that include a Marriott hotel in Florida, an FBI building in Alabama, a Lowe’s hardware store in California and a Kohl’s department store in Arizona are also part of the portfolio being marketed for sale.

Mitch D’Olier, president and chief executive officer of Kaneohe Ranch, issued a written statement describing the sale offer as part of a “variety of strategic alternatives” for the Castle Foundation and its affiliates.

“These options may include selling some or all of the owners’ real estate holdings in Hawaii and elsewhere, or retaining ownership of some or all of the real estate,” he said. “No decision has yet been made concerning whether any of these holdings will be sold.”

D’Olier, through a representative, said he would not comment further.

A sale, if made, would reconstitute the assets of Hawaii’s largest locally based private foundation, and potentially lead to a new vision for redeveloping much of Kailua’s commercial center.

Kaneohe Ranch produced its own long-range plan for Kailua in 2004 based on extensive community input, and over the past several years has invested more than $35 million in improvements that have included new shops and restaurants while trying to maintain Kailua’s character. A new owner conceivably might want to alter the plan.

Eastdil highlighted the opportunity to redevelop much of Kailua’s commercial center because several land leases there expire this decade.

No price was available for the offering, which includes all the properties together or the Hawaii properties separate from the mainland properties.

The Castle Foundation reported that the value of its assets in 2011 was about $150 million, which includes real estate and other investments.

The Castle Foundation’s sale effort is the latest in a string of big estate-like deals for Hawaii real estate holdings amassed by businessmen a century or so ago.

Among those other deals was Castle & Cooke’s sale of Lanai last year for several hundred million dollars.

In 2004, the Damon Estate sold about 200 acres in Mapunapuna and Kalihi Kai for $480 million in a deal brokered by Eastdil.

Campbell Estate has sold several thousand acres of mostly farmland in Kunia and Kahuku over the past several years in connection with converting to a private company.

And Victoria Ward Ltd., formerly headed by D’Olier, sold Ward Centers on 65 acres in Kakaako for
$250 million in 2002.

Mike Hamasu, research and consulting director for commercial real estate firm Colliers International in Ho­nolulu, said now is an opportune time to seek a buyer for something like the Castle Foundation portfolio because interest rates are low, the economy is growing and there’s little Hawaii commercial property available.

“There’s bound to be a huge amount of interest,” he said.

A sale would generate a big infusion of cash into Castle Foundation, which awards annual grants to nonprofits that benefit Hawaii residents.

The foundation was established in 1962 by Harold Kainalu Long Castle, who purchased 9,500 acres in the Kailua area in 1917. Castle helped establish Kailua by donating land for churches, Castle Hospital, schools including Castle High School and Hawaii Loa College, and the land that became Marine Corps Base Hawaii.

Castle died in 1967, and contributed much of his real estate assets to the foundation, which earns and distributes income from the property holdings.

The foundation to date said it has awarded about $176 million in grants, including more than $60 million to organizations serving Windward Oahu.