Clarence Thomas and Bohemian Grove: What goes on at the all-male club?

Bohemian Grove, an all-male club for the rich and powerful, is in the news after it was reported that Supreme Court Justice Clarence Thomas visited the retreat with a billionaire friend.

A report by investigative news outlet ProPublica revealed that Justice Thomas accepted luxury trips around the world from billionaire Republican donor Harlan Crow. This included a visit to the Bohemian Grove.

Located in remote Sonoma County, north of San Francisco, Bohemian Grove's exclusivity and secrecy has inspired both protests and conspiracy theories.

The club that runs the retreat insists that business talk is forbidden. But reports say some of America's most powerful men have cut deals and networked amid an odd assortment of performances and rituals at the 150-year-old club.

How did it start?

The Bohemian Club was started by journalists, artists and musicians in San Francisco in 1872 - Mark Twain was an early member.

Bohemian Club members pictured in the early 20th Century

The two-week encampment at Bohemian Grove, a 2,700-acre wooded rural retreat, began six years later as a send-off for an actor who was moving to New York City.

Over time the artsy roots of the club expanded to include businesspeople and politicians. Members are allowed to bring guests but the gathering is closed to media and outsiders.

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Who belongs to the club?

Although the list of 2,500 members is secret, some information has filtered out, and the club maintains a bare-bones website.

Past members include presidents Herbert Hoover, Ronald Reagan and Richard Nixon, along with a litany of famous writers, actors and businessmen.

The Grove's motto, taken from A Midsummer Night's Dream, is "Weaving spiders come not here" - an admonition against business talk that has been often ignored.

Most famously, a planning meeting for the Manhattan Project in 1942 held at the Grove later led to the development of the atomic bomb.

What really goes on there?

The two-week encampment reportedly involves stage performances, rituals, a lot of drinking and open-air urination.

Over the years, anti-capitalist, environmental and anti-nuclear demonstrators have protested against the event, although a local news report last year noted the protests have become smaller over time.

Journalists have repeatedly tried to infiltrate the gathering.

A 1989 article in Spy magazine called the encampment "the most exclusive frat party on earth" and detailed a speech by Mr Reagan, who had just left office.

In the year 2000, conspiracy theorist Alex Jones snuck in and recorded one of the club's rituals, the burning of an effigy.

He made a documentary filled with lurid accusations about grand plots and human sacrifice.

He was accompanied by the journalist Jon Ronson who had an altogether different take. He later wrote: "My lasting impression was of an all-pervading sense of immaturity… I wondered whether the Bohemians shroud themselves in secrecy for reasons no more sinister than they thought it was cool."

The club is currently advertising vacancies for bartenders, security officers and other jobs for this summer's events - what is not known however is who will be the attendees.