MARIN COUNTY, Calif. (KGO) -- Mt. Tamalpais in Marin County is one of the Bay Area's most popular outdoor destinations. World class views, redwood groves, waterfalls, and even an outdoor theater draw about 3 million people a year, but most of them never see a mysterious jumble of ruins on the mountain's West Peak.Marin resident and filmmaker Gary Yost first stumbled on the weird spot when he was hiking 20 years ago."It was a big mystery. It's kind of like a black hole, right in the center of this national and state park," remembers Yost.Yost did some research and learned the 100-acre patch of ruins was all that was left of an old U.S. military base. It was a mostly secret operation that began in the early 1950's when the Army and Air Force built a radar station on Mt. Tam to watch for Russian bombers that might fly in over the Golden Gate.Yost has now become an expert on the abandoned military site and a leader in a community effort to restore what he considers a massive scar on the natural landscape. Yost also produced an award winning documentary called " The Invisible Peak " that tells the story of what happened when the military moved on to the mountain.The documentary includes dramatic animation that shows how the military blasted, bulldozed and removed half a million tons of rock and dirt, shaving 30 feet off the top of the mountain. On top of the flattened peak, they built two big radar domes, tracking stations and barracks to house hundreds of technicians and soldiers."The Cold War was a real thing at that time, so nobody really wanted to deny the military that opportunity," according to Yost.But by 1980 the West Peak base was obsolete, and the military moved out. After originally promising to restore the mountain, the Army and Air Force just left the base standing empty.Within a short time, local citizens started to tear down the buildings. Janet Walker with the Tamalpais Conservation Club was one of those who did the work. "We felt it was very important that we should help clean up this mess that the Air Force had left because it was so unsightly and it didn't belong on the mountain," said Walker.The team managed to tear down three buildings, but had to stop after the discovery of toxic asbestos. The rest of the dilapidated base sat empty for 15 years until government agencies finally did some more demolition. But the site is still covered with a desert concrete and remains, including building foundations, power lines, fencing and pipes.The effort to restore the West Peak is spearheaded by a coalition of public and nonprofit agencies that work together under the name " One Tam ." They include the Marin Municipal Water District. Mike Swezy, who just retired from the water district, has been pushing to bring back the West Peak's natural eco-system for years."We won't be able to put it back together exactly the way it was, but we will be able to naturalize it in some fashion and kind of create the canvas for nature to rebuild itself and reestablish native vegetation," Swezy said.The ruins are at the top of the watershed, where each bit of open space is critical to catch and filter rainwater as it drains into Marin County reservoirs. So removing the pavement is a priority. The team also wants to restore habitat for rare native plants and improve public access.Marin County state and national park departments are also part of the One Tam coalition, trying to generate funding and community support for the restoration. The project would cost an estimated $13 million, which would come from grants and private donations.Claire Mooney with the nonprofit Golden Gate National Parks Conservancy says the current proposal is to remove almost all the ruins, leaving just a couple of old building foundations. Mooney said those would be used "as opportunities to talk about the history of the Air Force station and why we are working so hard to restore this site."An interactive exhibit about the West Peak history and restoration project just opened at the Marin Art and Garden Center in Ross. It will run through March 16, 2019. Thursday night (Jan. 31) the restoration team will be there for a special public presentation. Click here for more information.