The view became much less scenic in 1996, when the Coliseum completed a towering upper deck over the outfield intended to attract football’s Raiders back to Oakland from Los Angeles. Everyone, including A’s executives, call it Mount Davis, after Al Davis, the Raiders owner who died in 2011. It is an unsightly heap of concrete that blocks the view of the Oakland hills, and the A’s have mostly laid a tarp over its roughly 8,000 seats since 2006. But on Wednesday, when the A’s host the first playoff game at the Coliseum in six years, the tarp is coming off, expanding the stadium’s capacity by 17 percent to 55,000 fans, nearly the most in the majors .

Joey Mellows, a 34-year-old teacher from Portsmouth, England, who quit his job to visit all 30 M.L.B. ballparks this summer, said that while he was wowed by the classic parks, nothing could match the Coliseum’s atmosphere. “It’s grungy and it’s grimy and it’s got many quite obvious imperfections,” he said. “But personally I find that gives it an authenticity and a character that sometimes is lacking in the more sheeny, shiny, brand-new ballparks.”

Dave Kaval, the A’s president who has staked his job on finding the team a new home in Oakland, said that, character aside, the A’s can’t survive in the Coliseum. He is well-versed in the history of ballparks — he wrote a book on his own 30-park tour in 1998 — and argues that while multipurpose stadiums away from urban cores made sense during the 1960s suburb boom, they are now outdated. Although the Coliseum connects to public transportation, that isn’t enough. People are now clustering in urban centers, he said, and teams need to meet them there to succeed.

“There is an urban renaissance, especially among younger millennials,” said Kaval, reclined in his box during a recent weeknight game. “So that’s one reason we’ve been focused on the downtown waterfront location. When you look across baseball and sports, that’s a winning formula, especially as baseball looks to attract younger fans.”