The Foo Fighters recorded Sonic Highways in 8 different cities. In a new video for Jimmy Fallon, Grohl gives a glimpse into the process the band used for the disc.

He waxed on about I am a River, a tune he penned as the closer for Sonic Highways and it's filled with references about the Big Apple.

"[The lyric] 'I found a secret behind a Soho door' is referring to the Magic Shop studio and how it's just this one tiny door on the street," he says. "You would never know it's a studio."

Grohl also explains the origin of the title, which refers to Minetta Creek -- a stream that runs underneath New York City.

"I thought it was a beautiful idea that there's something natural and prehistoric that runs underneath something as monolithic and futuristic as New York City," he says. "And maybe we're all connected by something like that."

Foo Fighters recently performed "I Am a River" -- complete with a string section -- on The Tonight Show.

See Dave on Fallon's How I Wrote That Song.

Foo Fighters I am a River.

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