A Subway has rolled into the train station. A sandwich shop, that is.

The chain celebrated the opening at Union Station recently because it is its 600th sandwich shop in the L.A. area. But the owner of the franchise celebrated just for opening at all. It took him more than four years.

The site of the sandwich kiosk was the brainchild of Parvis Mohammadi, who now operates eight Subways throughout Los Angeles County. He had the inspiration while vacationing in Italy six years ago.

“At the Rome train station there were a lot of boutiques and brand names,” Mohammadi said. “Why not here?”

He first submitted his plan in 2006, but Denver-based ProLogis, which owned Union Station at the time, was cold toward retail and rejected the plan. Mohammadi repitched the idea every six months, but was always turned down. TPG Capital Partners LLC, a San Francisco-based private equity firm that bought the station last year, was more amenable.

That wasn’t Mohammadi’s last hurdle, though. The Los Angeles Cultural Heritage Commission, which oversees preservation of historic and cultural monuments including Union Station, played hardball with the restaurant’s aesthetics.

“Only specific colors and materials go with the vocabulary of the station,” said Lambert Giessenger, historic preservation architect at L.A.’s Department of City Planning. The commission required a bronze sign and a dark wood finish in order for the shop to open Dec. 28.

The Union Station site is an example of Subway’s strategy of placing itself in places you might not expect. For example, the chain plans to open Subways at Disneyland, Hermosa Beach Pier and Cedars Sinai Hospital, said Hardy Grewal, president of OhCal Foods, which sells franchises in Los Angeles and Orange counties and elsewhere.

The Union Station location, next to the Red Line entrance, has been busy, according to employee Josylene Mays, who transferred from a Chinatown franchise.

“There we had rush hour,” she said. “But here it’s like that all day.”