Now people don't really know what to make of it, but it's survived the first two years of the new owner, Arte Moreno, so it's probably not going anywhere.
"It gives this place some life," says groundskeeper Mike Dutch. "It's definitely a part of the culture of this stadium now."
A big part of that culture are the waterfalls and fireworks that shoot out of the rocks during an Angels rally or after a hometown home run.
But it's a lot more fun under the rocks, and a pregame trip to the world beneath them is almost like a school field trip, a fact-finding tour that yields quite a few educational surprises.
You have to walk all the way around the stadium, then exit a tunnel from a service hallway until you're in a driveway-type area that leads out through the outfield wall to the field. Make a left turn into a doorway and you're under the rocks.
The first thing you see are shovels, rakes, hoes, lawnmowers and other gardening equipment that tells you pretty clearly that you've stumbled upon the headquarters of the Angels' grounds crew.
They're a highly respected bunch, led by field and ground maintenance manager Barney Lopas, and they're proud of their little hangout beneath the rocks.
Dutch was kind enough to give MLB.com a tour of their lair and was happy to point out the small disco ball hanging in the shed that houses most of the lawnmowers.
Ambling past a Pop-A-Shot basketball machine ("It's so the kids don't get bored," Dutch said), he opened the door to what the grounds crew lovingly calls "Club Rock," an all-purpose hangout where the crew spends the lonely hours of the game when it is not raking or dragging the infield to perfection.
Club Rock is about as plush as you could expect a room to be when it's inhabited by guys who make a living getting dirt and grass stains all over their bodies. There are three sofas surrounding a big-screen TV, there's a card table, lockers, a video-game machine and a water cooler.
Then there's Lopas' office, which is spacious and air-conditioned. It's good to be the king.
"We have a lot of fun down here," says crew member Doug Forsyth. "After the game, this is where we have our soda pops."
There's a cooler of said soda pops out in the hallway, but the crew waits until its work is done before indulging.
During the game, the groundskeepeers are not always the only ones in the room.
"The bullpen guys sometimes come over here and relax on the couch," Forsyth said. "Percy [Troy Percival] used to nap here sometimes. So did [Mike] Holtz, [Al] Levine and Shige [Hasegawa]."
Since the room has that huge TV, it's easy for the crew members to tell the relievers to get up and at 'em if it looks like they'll need to be called on.
"The guys on this year's team don't do it, though," Forsyth said, probably not wanting to get anyone in trouble.
One of the true prizes in Club Rock is the Angels poster that has been signed by practically every Angels player in the last 10 years and Moreno himself -- three times.
"It's our own little world," Dutch said. "We're proud of it."