A colonial-style house has been built in front of Cardiff University's Main Building.
The building reminiscent of the French-Spaniard style seen in places like New Orleans was put up on the greenery in front of the historic Main Building.
The impressive building has been constructed for Sky One series A Discovery of Witches.
A crew of workers were seen at the site on Thursday, constructing the build, which copies architecture familiar with southern US states and some Australian cities, and adding fake greenery to the branches of bare trees.
A Discovery of Witches is a Sky TV series based on the books by Deborah Harkness. There has already been one series of the show aired on TV, while the second series is due to hit UK screens in January.
A Discovery of Witches features The Crown star Matthew Goode and Australian actress Teresa Palmer who was in Oscar-nominated movie Hacksaw Ridge and thriller Lights Out.
Previous series have also been shot in Wales, including stunning scenery of the Brecon Beacons and at Wolf Studios in Cardiff and Pinewood Studios Wales.
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One Twitter user who spotted the building said: "It's definitely New Orleans. I saw something from an extra. They were told to dress for 22° New Orleans tomorrow.
"I'm thinking this could be for 'A Discovery of Witches', though I'm hoping it's Doctor Who."
A spokesman for A Discovery of Witches confirmed filming for season three had begun and that safety protocols, including twice-weekly tests and bubbles were in place to make the production as Covid-safe as possible.
The show is produced by Sky TV and Bad Wolf productions, who are the makers behind His Dark Materials which was also filmed in Wales.
