The architecturally unique house in the Malibu hills is not Clark's main residence -- that one is across Pacific Coast Highway on the beach.
The house Clark and his wife Kari have always called "Bedrock" features vaulted ceilings in the living and dining rooms, a fireplace in the bedroom and lots of glass to showcase the 360-degree mountain and beach views from every room, limelife.com reported Friday.
The structure and texture of the interior resemble a cave but has amenities the cartoon Flintstones, Fred and Wilma, never would have imagined.
The real estate agent handling the house listed it this way: "Malibu celebrity romantic retreat. This is art as architecture at it's finest. This truly magical retreat offers seclusion, privacy & serenity yet minutes from the beach."
Bedrock -- complete with wine cellar -- is listed at $3.5 million, the Los Angeles Times said.