James Martin/CNET

SAN FRANCISCO -- Something big and mysterious is rising from a floating barge at the end of Treasure Island, a former Navy base in the middle of San Francisco Bay. And Google's fingerprints are all over it.

It's unclear what's inside the structure, which stands about four stories high and was made with a series of modern cargo containers. The same goes for when it will be unveiled, but the big tease has already begun. Locals refer to it as the secret project.

Google did not respond to multiple requests for comment. But after going through lease agreements, tracking a contact tied to the project on LinkedIn, talking to locals on Treasure Island, and consulting with experts, it's all but certain that Google is the entity that is building the massive structure that's in plain sight, but behind tight security.

Could the structure be a sea-faring data center? One expert who was shown pictures of the structure thinks so, especially because being on a barge provides easy access to a source of cooling, as well as an inexpensive source of power -- the sea. And even more tellingly, Google was granted a patent in 2009 for a floating data center, and putting data centers inside shipping containers is already a well-established practice.

Whether the structure is in fact a floating data center is hard to say for sure, of course, since Google's not talking. But Google, understandably, has a history of putting data centers in places with cheap cooling, as well as undertaking odd and unexpected projects like trying to bring Internet access to developing nations via balloons and blimps.

Hangar 3

Sometime late last year, a company began a substantial project inside a cavernous building on Treasure Island known as Hangar 3.

Since then, Hangar 3 and the areas immediately adjacent have been under various stages of lock-down. Thanks to Google's own satellite imagery, though, it's possible to get a glimpse of the early stages of the project, and much of which was being worked on outside the building but shielded behind a long security fence.

Screenshot by CNET

It's also possible to tell from that imagery and by visiting Treasure Island that whatever was under construction in the area outside Hangar 3 has since been moved to a floating barge alongside the pier adjacent to the property, which is off-limits to the public and guarded by private security.

The barge is 250 feet long, 72 feet wide, and 16 feet deep, and was built in 2011 in Belle Chasse, La., by C & C Marine and Repair. Its registration number is BAL 0010. Behind it is a perfect view of the new eastern span of the San Francisco Bay Bridge. On top is a four-story-tall modular building made from shipping containers and sporting 12 tall white spires that look like they could be anything from masts to flagpoles to antennas. The containers each have three narrow slits for windows, and there is a stairway on the northeast corner that goes from ground level to the top. There's also one container on that side that slants to the ground at a 45-degree angle. Wrapped mostly in dark netting, the structure doesn't reveal what's inside.

James Martin/CNET

Joel Egan, the principal at Cargotecture, which designs custom cargo container buildings, said the structure looks like a data center. "The cutouts in the long walls of the containers, when they line up, they make hallways," Egan said. "You could put all sorts of mainframes into the containers...It doesn't have enough windows for an office building."

Egan also said that putting a data center on a barge would provide access to abundant water -- a key for cooling large numbers of servers.

Asked if the theoretical concept of a floating data center made practical sense, Jonathan Koomey, a Stanford research fellow and expert on data centers responded by listing a number of advantages such a system would offer. Although saltwater could be problematic as a cooling source, he said, it's a surmountable problem. "It wouldn't surprise me at all," Koomey said, before seeing any pictures of the project on the barge, "if there were a bunch of containers, and it turned out to be data center." After being shown pictures of the barge, however, Koomey said that there was nothing conclusive in them to indicate that it was a data center.

But companies like Dell, Hewlett-Packard, Microsoft, and others have been installing specially built data centers in shipping containers for some time because they're easy to deploy. And Google even has a patent for the concept.

Perhaps more persuasive is that in 2009, Google was granted a patent for a " water-based data center," defined as a "system [that] includes a floating platform-mounted computer data center comprising a plurality of computing units, a sea-based electrical generator in electrical connection with the plurality of computing units, and one or more sea-water cooling units for providing cooling to the...computing units."

Google

The patent further suggests that "the computing units are mounted in a plurality of crane-removable modules," that "the computer data center comprises a floating-platform mounted data center," and that "the modular data centers may be arranged in a two-dimensional or three-dimensional grid. For example...two rows that each contain two containers...Those modules could also be stacked two or more high."

The patent was granted to three men -- Jimmy Clidaras, David Stiver, and William Hamburgen, all of whom still work at Google. Only Clidaras replied to requests for interviews, although he wasn't immediately available to comment.

Time magazine, for one, thought so much of the concept that it named Google's idea one of its "best inventions" of 2008.

Why? Google's patent spelled out some of the most valuable advantages: Because the system is built from modular, standard-size shipping containers, it's easy to deploy, via ship or truck, to areas that are in most need of Internet infrastructure; there's little-to-no pollution created by wave-generated energy; and a floating data center could produce plenty of power via wave energy at a distance of 3 to 7 miles offshore, and in 50 to 70 meters of water.

The structure built on the barge could easily be following just this concept. And it could well be the answer to this article, which pondered, "What Happened to Google's Floating Data Center?"

Hunting for the Google connection Although Google has not confirmed any projects on Treasure Island, which is owned by the US Navy and subleased by the city of San Francisco, ample evidence suggests that the company is behind whatever is going on inside Hangar 3 and on the barge at the southeastern end of the island.

When asked by CNET, Treasure Island director of island operations Mirian Saez said that Google had not leased Hangar 3. She said that a company called By and Large LLC was the new major tenant of the building.

Screenshot by CNET

By and Large has a miniscule online profile, and no clear ties to Google. The lease, provided by Saez, identifies two men, Mike Darby and Kenneth Yi, as By and Large's official representatives, as well as a phone number for the Delaware-registered company. Darby told me he wasn't associated with By and Large. Yi, who is the signatory on the lease, couldn't be reached for comment.

Even so, a former Google employee who requested anonymity said it "makes perfect sense" that the tech giant would set up an innocuous LLC to officially run a big stealth project. Saez said that a man named Tim Brandon was the point of contact for By and Large, and provided a phone number. Punch in the digits provided by Saez and you'll hear, "Thank you for calling Google. The number you dialed is no longer in service." In addition, Brandon's LinkedIn profile identified his current position as "Senior Transaction Manager, CBRE @ Google" and his top responsibility as "Lead and manage all acquisition and disposition activity for Google's Silicon Valley portfolio."

Until I contacted him, that is. After I messaged him through LinkedIn and sent him an e-mail earlier this week -- without getting a response -- Brandon's profile now lists his current position as just "CBRE" and his top responsibility as "Lead and manage all acquisition and disposition activity for Silicon Valley portfolio."

Screenshot by CNET

CBRE is short for CB Richard Ellis, which identifies itself as "the world's largest commercial real estate services firm serving owners, investors and occupiers." A CBRE spokesperson confirmed Brandon's employment but said the company doesn't talk about clients. The company routinely assigns its people full-time to clients for any number of tasks or services, he said. In such cases, those people's professional profiles would list them as "CBRE @" the specific client's name. CBRE's Website lists Brandon as located in Mountain View, Calif., home to Google headquarters and no CBRE offices.

By and Large is both the official Hangar 3 tenant and the owner of the barge. An online document showed that By and Large is the owner of the freight barge that holds the structure. A representative at C & C Marine and Repair, which built the barge, told me that a vessel like BAL 0010 is capable of going "anywhere the owner can take it," including into open water. That suggests that whatever is being built on the barge could well be intended for waters well beyond Treasure Island and San Francisco.

James Martin/CNET

Even without a formal link to Google, I did find less official but persuasive evidence. A woman who works at the Oasis Cafe, down the street from Hangar 3 said that she had frequently served people wearing Hangar 3 badges who paid with "Google credit cards." She also said that whatever has been going on inside the building and on the barge is very hush-hush on the island and that even the people she suspected are Google employees don't "know what they're working on."

James Martin/CNET

When I met someone working in a section of Hangar 3 that's separate from the main part of the building and inquired what building it was, the man asked who I was looking for. I answered "Google," and without hesitating he said I needed to go to a main entrance a bit further down the side of the structure. That entrance was manned by a security guard and had two cameras mounted above the entryway. A security supervisor turned me away when I asked to visit Google or talk to Tim Brandon. Upon returning to Hangar 3 a couple of days later with a CNET photographer, we were watched closely by two people, including one with a big set of binoculars.

A sign on one entrance to Hangar 3 reads, "You are entering a secure building. Please prepare to surrender your smart phone, camera phone, camera, and or any other audio/visual devices."

Daniel Terdiman/CNET

Chris Childers, a Treasure Island local, told me that although he had never seen the word "Google" anywhere in or around Hangar 3, people have been talking about Google being in the giant building, and working on the barge, for months.

In fact, Childers said, the tenant had taken over the Hangar 3 parking lot last December, and for months had very tight security around it. "I heard it was a Google project," Childers said. He also recalled the long security fence around the Hangar 3 property that is visible in Google satellite imagery, as did an artist who works close to Hangar 3.

Childers told me that a woman at a Treasure Island bus stop that he suspected was a Google employee had told him, about what was going on inside Hangar 3 and on the barge, "I can't tell you [what the project is, but you'll see it soon enough, and it'll be really cool." He also said that the woman told him that the massive project being built on the barge had likely been built piecemeal inside Hangar 3 and that "'I can't believe we built it all inside'" Hangar 3.

Larry and Sergey, and anyone else who might have knowledge of this project, we'd love to hear the full story.

Update (Sunday, 5:45 p.m. PT): This story now more accurately represents comments made by Stanford researcher Jonathan Koomey.