Star Trek: Discovery has just finished filming...in a Canadian former prison.

A piece on Kingstonist.com out of Kingston, Ontario, says that for the past two weeks, the cast and crew of Discovery have been filming scenes for the upcoming season three, in Kingston Penitentiary. The former prison, known as Kingston Pen, is one of Canada’s oldest and most notorious. It’s also home to some remarkable architecture. The site, which opened in 1835, was named a National Historic Site of Canada in 1990.

Alex Jansen, Film Commissioner with the Kingston Film Office spoke of the secrecy with which he treated the production. “The Kingston Film Office did indeed host Season Three of Star Trek: Discovery over the past two weeks,” he said. “We kept everything entirely confidential at the express request of the production, but I can confirm that we hosted them for five days of pre-production, two days of shooting, and they’re in the process of finishing three days of wrap-up.”

Kingston Pen was an operational prison as recently as 2013, according to Wikipedia. But now it’s a popular film location; recent productions filmed there include not just Discovery, but DC’s Titans, and Murdoch Mysteries, as well.

The Kingstonist piece says that Jansen is unsure when the Discovery scenes filmed there will air. Star Trek: Discovery is currently expected to come out in early 2020.