Mirror Universe
(coexisting on another dimensional plane)

Harlak was a planet in the mirror universe, with at least one moon. Its surface held the ruins of large cities.

In 2254, the Resistance established a camouflaged base in the northern hemisphere of this planet. For two years, the base coordinated the rebellion against the Terran Empire before Imperial Intelligence discovered its location in 2256. Captain Michael Burnham of the ISS Shenzhou was ordered to destroy the base and kill all rebels on Harlak, but unknown to them Burnham had been replaced by her counterpart from the prime universe. She instead chose to warn the rebels, who began evacuating.

Before the evacuation could be completed, however, the ISS Charon entered the system and carried out Burnham's mission, unleashing an orbital bombardment that devastated both the base and a wide expanse of the planet's surface. (DIS: "The Wolf Inside")

For the exterior scenes, showing the surface of the planet, they were shot at Lafarge Quarry outside the city limits of Toronto. (After Trek: "Episode 10")