CHICAGO (CBS) — Remember the magical moment from Harry Potter where the secret door to the Hogwarts Express is hidden behind a brick wall? Turns out there’s another door to Hogwarts in Chicago.

A CTA rider spotted it on his morning commute. And his tweet about it cast a spell on author J. K. Rowling herself.

“It’s completely surreal,” said CTA rider Michal Wilczewski.

As surreal as Harry Potter’s wizarding world.

CTA rider Michal Wilczewski noticed a familiar image on his morning commute: a door to Hogwarts, the wizarding school,  drawn in chalk on the side of a Bucktown building.

The Harry Potter fan snapped a pic and tweeted it to author J.K. Rowling.

“I knew she had a history of interacting with fans and responding to people’s questions,” said Wilczewski.

He tweeted “can you tell me more about this door to Hogwarts at the Damen Blue Line stop in Chicago?”

Minutes later, the famous Potter author with 14 million Twitter followers answered back.

“It’s for exchange students from Ilvermorny. Duh.”

Ivermorny being the North American wizarding school.

“I literally started to shake,” he said.

The University of Illinois at Chicago history instructor said he was so excited about Rowling’s response he missed his stop.

“All of us grew up with this book, so seeing this might be a little bit of magic in people’s lives was a lot of fun,” said Wilczewski.

Rowling’s response to his tweet now has more than 19,000 likes and 2,000 retweets.