In downtown Seattle, CenturyLink Field is filled with a capacity of 67,000 screaming fans. These fans are called the 12th man, and they show up in full force, wherever the Seahawks play.
CenturyLink Field is one of the hardest places for opponents to play because it is one of the loudest stadiums in the NFL. The loudest crowd noise in CenturyLink was registered at 137.6 decibels according to Guinness World Records. Just for reference, a jet at 100 feet away is about 140 decibels. There's a reason why Marshawn Lynch's run against the New Orleans Saints was called Beast Quake, because it literally caused an earthquake in Seattle.
While the Seahawks currently use the stadium, they aren't the only professional team to call CenturyLink home. The 2016 MLS champions, the Seattle Sounders FC, play all of their home games in the Emerald City. With players like midfielder Osvaldo Alonso and forward Clint Dempsey, the Sounders are back in the MLS Cup Playoffs.