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Source:The New Democrat 

The old Oakland Coliseum was a strange place for football. Because it was basically a baseball park that was renovated so the Raiders could play football there. And then later so the Invaders could play football there as well. But the old Oakland Coliseum was much better suited for baseball than football and had a better baseball feel. The Oakland Coliseum looked strange for football, because the Invaders played during the baseball season when the Athletics were playing. And you had the outfield seats of the baseball park essentially on the sidelines of the football field. And the Coliseum was an open air ballpark before the Raiders came back in 1985. Which meant the outfield was a single deck. Most football stadiums the sidelines have multiple decks, because those are where the best seats are for the game. And teams want to be able to seat as many people there as possible.