Tinseltown may be known for big stars and that famous sign on a hill, but when all is said and done, its real treasure is its movies - as in, actual film.

For years, the Academy of Motion Picture Arts and Sciences - the folks behind the Oscars - has made it its business to preserve tens of thousands of movies, and these days, it does so at the Pickford Center in Hollywood, an old TV studio.

Now, the Academy Film Archive keeps more than 76,000 titles locked away in cold storage in giant concrete vaults, safe from earthquakes and fire, all so that future generations can be sure to enjoy watching the great (and even the not-so-great) flicks this town has produced.

Films are archived on large sets of shelves in three cold-storage studios. Though there is no specific order in which the movies are stored, they are all digitally coded, so archivists can find any title they want quickly. Pictured at left: Multiple reels of a 70mm print of "Lawrence of Arabia."

It's been more than half a century since films were made using highly-flammable nitrate stock, but there are still countless movies in existence that used the unstable material. Nitrate stock burns uncontrollably if it ignites, but it also can decompose - and once it does so, the only way to stop it is to cut out the ruined elements, which meld into what is called a "hockey puck," as seen here.

Academy Film Archive director Michael Pogorzelski explains the preservation system inside one of the cold-storage vaults.

A look through the grated floor of the second story of one of the vaults at films stored on the first floor.

The famous gold statue, writ large, stands guard inside the Academy of Motion Picture Arts and Sciences' Pickford Center, home to the Academy Film Archive in Hollywood.

A reel of the 1982 Jessica Lange film "Frances" is stored in what's known as a molecular sieve to protect it from the breakdown of acetic acid. The sieve sucks up the acid released during the decomposition process.

On a shelf, a look at three different sizes of film stock in the archive's collection: from left, 16 mm, 35 mm, and 70 mm.

Several reels of "2001: A Space Odyssey" sit on a shelf at the Academy Film Archive.

Several reels of "Spider-Man" sit in plastic cans on a shelf in the archive.

The Academy Film Archive stores films in cold-storage vaults at 50 degrees Fahrenheit and 25 percent relative humidity. Because of that, when it is necessary to remove reels for any reason, they must first be acclimatized before entering normal environmental conditions. As a result, they are stored in this interim area for 24 hours, covered by plastic in case a fire causes sprinklers to go off.

Because water is just as bad for film stock as is fire or smoke, there are no water pipes anywhere inside the vaults. Instead, the Academy utilizes a fire suppression system called Inergen, which instantly converts oxygen in the air to carbon dioxide. That leaves no fuel in the air for fire, but enough oxygen for someone inside the vaults to breathe long enough to escape.

The Academy keeps this phalanx of tanks in the basement of the building, always at the ready to completely fill a vault with Inergen in the case of a fire. However, two different sensors in the vault must both be triggered in order to release the material, to prevent a costly false alarm.

A stack of nitrate film reel cans on a table inside the office where archivists work with the highly-flammable material.

A very old and rusty nitrate film reel can.

The Academy Film Archive, in addition to maintaining more than 76,000 titles on film stock, also has machines that can be used by researchers and others to play back the movies, including this Moviola.

The Academy Film Archive also keeps thousands of film titles on various types of video tape. This is a look at some of the many different kinds of video tape formats in its collection, including a circa-1986 D1 (far right) to an HDCam SR (left).

This is a copy of "The Bridge over the River Kwai" on an RCA CED (a Capacitance Electronic Disc) video disc, which replayed information via a diamond stylus in a groove, similar to a phonograph needle. CEDs failed in the market in part because the video quality did not match optical laser discs.

Pictured: A cart full of various playback decks used when someone needs to review old video tape. The Academy Film Archive tries to keep a complete set of these machines, as well as others from which to take parts, to ensure that it will continue to be able to play back any tape in its collection.

By CNET.com's Daniel Terdiman
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In Hollywood, keeping Tinseltown's treasures safe forever (CNET article/video)