Though these days the Oscar-nominated actor is best known for being Michael Douglas' father, the fact is that he'sa legend in his own account, having starred in some of the biggest classics of the Hollywood golden era - but now it seems like, in his youth, Kirk Douglas' Playboy fascination was a part of how he spent his days!

Jack Nicholson has been one of the most iconic bachelors in Hollywood for the past four decades or so, and his Mulholland Dr. home in Santa Monica was where Roman Polanski's infamous child molestation case in the 70s; now, it seems like Kirk Douglas' Playboy secret was right along Nicholson's.

According to website Haaretz, blueprints of the Mansion where Hugh Hefner lives with his wife have just been revealed, and it seems like Kirk Douglas' Playboy involvement was far greater than just popping into parties every once in a while.

Seemingly, Kirk Douglas' Playboy secret was only part of a larger net of A-list actors from the 70s, as it seems there was an exclusive group of actors from the decade that had privileges over Hefner's home, so much so that they had access to it through subterranean tunnels, The Telegraph reports.

The whole thing came out through a post in the Playboy website entitled "So, There Were Tunnels to Celebrity Homes Below the Playboy Mansion," as a writer revealed that, looking through the magazine's archived photo material, he found pictures of an excavation project in the mansion from the late 70s, and later discovered through the Mansion's general manager that Hefner had built tunnels in the late 70s to connect to the homes of some of the biggest names in Hollywood at the time - including a Kirk Douglas Playboy one.

Besides Douglas and Nicholson, other stars linked through the tunnels are James Caan and Warren Beatty, both big names at the time; in his youth, Annette Benning's husband was known as a player, having gone out with a series of Hollywood beauties including Diane Keaton, Julie Christie, Lana Wood and her sister Natalie - who, Hollywood legend has it, was sexually assault in her youth by Douglas.

It seems like the Kirk Douglas Playboy tunnel, along with all the other ones, were closed up in 1989.