Belvedere’s Lava House lots are listed for $30 million

The four vacant Belvedere Avenue lots where the late seat-belt manufacturer Jerry Ganz spent two decades fighting to build, the site of the ruin known locally as the Lava House, are for sale as one package for $30 million.

The parcels at 399, 401, 415 and 419 Belvedere Ave. total about 2.75 acres above Richardson Bay, with views of the Golden Gate Bridge, the San Francisco skyline and Mount Tamalpais. The Sarkissian Bullock Team of Golden Gate Sotheby’s International Realty listed the land in mid-September and publicized it in an Oct. 29 news release.

The lots will not be sold separately, said Kevin Daniel Dwyer, the brokerage’s chief marketing officer. The site remains fenced, and showings are limited to “vetted, qualified buyers,” whom the agents walk through the property themselves, he said.

The listing lands as a new wave of artificial-intelligence wealth builds around the bay. San Francisco-based Anthropic filed Oct. 26 to go public, with a listing expected as soon as mid-November, and designer Jony Ive, whose AI-device startup OpenAI bought for $6.5 billion in 2025, paid $43.5 million last year for Belvedere’s Locksley Hall.

Dwyer pointed to the same money.

“The influx of wealth and the emerging affluent in the S.F. Bay Area from the AI and tech sectors presents a once-in-a-lifetime opportunity for a qualified buyer,” he said in an email.

County records show 399, 401 and 415 are held by Belvedere 401 LLC, which took title in 2020 from the family’s 401 Belvedere Corp., and 419 by the Peggy Homestead Trust, a trust for Ganz’s daughter, Peggy. Stan Beainy, a longtime trustee for the family, died in December, and Ganz has also died, Dwyer said. The family is not available for comment, he said.

What a buyer could build

The lots are zoned R-15, Belvedere’s single-family district for parcels of at least 15,000 square feet. On any one lot, a home’s floor area may not exceed 33% of the lot or 4,850 square feet, whichever is less, though the Planning Commission can allow a larger house if it finds the lot has unusual features that lessen the impact of a bigger house, the extra space would not significantly block neighbors’ views or substantially reduce their privacy, and the house is appropriate in mass and bulk.

An architect the listing agents consulted expects the size of these lots to help.

“Because the lots are larger than the minimum requirement, there is a reasonable chance that an exception to total floor area for a larger home would be approved, though it is not guaranteed,” David Kotzebue of David Kotzebue Architecture said in a statement provided by the agents.

State law also lets each lot carry more than one home. A single-family lot can add an accessory dwelling unit inside the house or an existing accessory structure, a detached unit and a junior unit of up to 500 square feet carved from the home, for as many as four homes per lot, or 16 across the property.

Belvedere caps a standard detached unit at 850 square feet, or 1,000 square feet with two bedrooms. Under the city’s size bonus, adopted in 2025, an owner who agrees to keep the rent affordable to low- or very-low-income households can build up to 1,000 square feet, or 1,200 with two or more bedrooms.

Belvedere’s housing element, the state-mandated plan that won certification in February, counts the four lots as one future home each, all at above-moderate income levels. If a buyer combines them for fewer homes, the state’s no-net-loss law can require the city to show capacity for the difference elsewhere.

Planning and Building Director Rebecca Markwick said the city would work with its housing attorney to determine how to prevent a net loss. No applications or approvals are active on the lots, she said, and any project would need a geotechnical report and approval from the Bay Conservation and Development Commission, the same as any new construction on a Belvedere Island hillside.

The price

Marin’s record home sale remains Locksley Hall at 440 Golden Gate Ave., which sold for $47.5 million in 2015. Ive’s 2025 purchase was part of a private, four-home, $73 million deal, and an estate at 20 Crest Road was listed in May at $50 million.

For land, the agents point to the $42.1 million the Trust for Public Land paid in 2024 for Easton Point, the 110-acre Martha property on the Tiburon Ridge, which they call the most expensive land sale in Marin County history.

Two of the four Belvedere Avenue lots have sold before. In May 2015, 401 Belvedere Corp. and the Peggy Homestead Trust sold 415 and 419 for $8.65 million to a trust of Howard R. King, and the sellers carried a $6.06 million loan, county records show. In October 2017, the King trust deeded both lots back in lieu of foreclosure, with about $6.1 million still owed.

Dwyer said his team was not involved in that transaction.

Decades of fights

Ganz, who made his fortune manufacturing seat belts in Chicago, began buying land on the Belvedere shoreline in 1972 and sought a 30,000-square-foot mansion that the city denied. He sued Belvedere twice, alleging a conspiracy, in suits that dragged on for nearly two decades. He lost one and won the other.

In 1986, he also bought the neighboring lot at 425 Belvedere Ave. from the widow of casino owner Bill Harrah and tore down the Harrahs’ home. The city approved a 16,000-square-foot glass house there in 1992, but work stopped after a landslide about two years later, and the house was never built.

Next door, Ganz’s crews had covered the slopes in lava rock, which The Ark reported was imported from Hawaii. Local lore holds it was barged in from the islands and cursed, after the legend that taking lava rock from Hawaii angers Pele, goddess of fire and volcanoes, and that the curse brought the landslides and the fire that later burned part of the property.

In the early 1990s, police answered a report of “satanic rituals” on the property; no one was arrested. In 1996, a fire that authorities said was possibly arson burned a garage and caretaker’s unit, and in 2004 a house at 401 was torn down, leaving its foundation and the lava rock behind.

Ganz walked away from 425 in 2008, when real-estate developer Jeff Paster bought it. Paster won approval in 2009 for a roughly 15,500-square-foot home there, opened it as a Marin Designers Showcase house and listed it at $45 million. It sold in September 2013 for $24.5 million, then a Marin record.

The rest of the land sat for decades as a maze of empty pools, grottoes and crumbling stairways, a magnet for teenagers and a recurring call for Belvedere police.

In December 2018, the Planning Commission voted 5-0, with commissioners Jim Lynch and Larry Stoehr absent, to approve a $600,000 cleanup. Crews working from March through December 2019 used a remote-controlled demolition robot and hauled about 500 to 600 cubic yards of rock and debris away by barge.

“Kids were cutting through the fence and going down on the property; we found drug paraphernalia. People were going down there and starting fires,” Beainy said as the work began.

A hog-wire fence went up under a condition that it stay only until the property is sold and a new project comes forward.

Reach Kevin Hessel at 415-435-2652.