There’s one tunnel — the tunnel — that every October gets even the subtlest of heartbeats pumping like a revved-up engine.

Both Texas and Oklahoma enter through that tunnel when they meet every year at the Cotton Bowl for the AT&T Red River Showdown, adding just another dynamic to the uniqueness of the historic rivalry.

“It’s an experience all on its own,” junior running back Chris Warren III said. “It’s definitely different.”

That tunnel is surrounded by nothing but a mass of crimson-clad Oklahoma fans every year. Traditionally, the Sooners’ faithful has controlled the south end of the stadium, creating an initial unwelcoming atmosphere for the Longhorns when they take the field. When Texas comes out of the tunnel, it’s like walking into the lion’s den.

“And then you step into the actual arena,” senior linebacker Naashon Hughes said, “and it’s divided, and you can just hear the fans going at it.”

First the boos — and surely a whole list of other explicit words and phrases that are not to be repeated — greet the Longhorns as they run onto the field. But once they cross the 50-yard line, the cheers and the sound of “Texas Fight” take over.

The Cotton Bowl’s seating is traditionally split at the 50-yard line for fans. It’s a natural recipe for some pretty compelling red zone trips for both teams. Texas fans get one side of the stadium, and Oklahoma fans get the other.

“The atmosphere is just incredible,” junior linebacker Malik Jefferson said. “It’s something that you can’t describe. You just have to experience it on your own.”

The State Fair of Texas that surrounds the Cotton Bowl only adds to the atmosphere. Junior safety DeShon Elliott — a native of Rockwall, which is about 30 minutes northeast of Dallas — said he used to go to the State Fair every year with his parents growing up. On game day, Texas and Oklahoma fans alike roam the grounds, standing in line with each other for Fletcher’s corny dogs, an array of fried food and, of course, beer.

Within the game itself, the constant momentum changes have also come to characterize the nature of the Texas-Oklahoma rivalry. At any moment, the game can flip on its head, sending half the stadium into a raucous and the other half into complete silence.

In the 2008 game, one of the most famous in the series, No. 5 Texas trailed No. 1 Oklahoma, 14-3, with 13:14 left in the second quarter. But then Texas wide receiver Jordan Shipley took back a kickoff 96 yards to the end zone to swing the momentum right back into the Longhorns’ favor. Texas, led by quarterback Colt McCoy, went on to take down the Sooners, 45-35, on that day.

“In this game, one play can change the whole game around,” Elliott said.

Texas owns an all-time record of 61–45–5 against Oklahoma. Come Saturday afternoon, another chapter will be written. The Longhorns could potentially open the floodgates on their season under first-year head coach Tom Herman with a victory over the 8-point-favorite Sooners.

“They’re gonna throw punches at us, we’re gonna throw punches at them,” Elliott said. “We gotta see who throws more punches.”