City hall in downtown Toronto has been given a Japanese-style makeover as it plays the role of Tokyo in an upcoming Hollywood action film. (CBC)

A downtown Toronto street has quietly been converted into Tokyo for an upcoming Hollywood action film.

Elizabeth Street, which runs just north of Toronto's iconic city hall, was decked out in Japanese signs Tuesday as the upcoming Hollywood film Silent Seas, also known as Pacific Rim, was shooting on location.

Signs, flags, even mailboxes on the street had a Japanese-style makeover for the action film, set for release next year. The movie's plot involves an alien attack on downtown Tokyo and the efforts of the human-piloted robots that struggle to repel them.

Overseeing the film is Pan’s Labyrinth director Guillermo del Toro. The film stars Idris Elba, known for his role as drug kingpin Stringer Bell in the acclaimed television crime drama The Wire.

Mailboxes with Japanese characters appeared in downtown Toronto on Tuesday. (CBC)

The directors spared no details in giving the streetscape an authentic look, everything from fake metro station signs to plastic cherry blossoms attached to the trees.

Everyone working on the film is staying tight-lipped about its details. They’re trying to keep filming locations secret, but some signs are too obvious to ignore.

"We now have a Japanese flag on our office, so I guess we're in the middle of it," said one downtown worker who spoke to CBC News.

The film is slated to continue shooting in Toronto through April.