Lactra VII was an inhabited M-class planet with Earth-normal atmosphere and gravity. It was home to the Lactrans, a highly advanced non-humanoid and telepathic species. There were several nearby bodies in the sky of Lactra VII. (TAS: "The Eye of the Beholder")
The planet contained at least one major city, considered admirable. Inside the city, and surrounding it up to almost a hundred kilometers, was a zoo in which a variety of lifeforms from other planets were kept in habitats manufactured to their needs. One such example included a desert and a rainforest separated by a river. The water discovered on Lactra VII was clear and palatable, but was, according to Spock, "too pure."
In 2293, the location of Lactra VII in the Milky Way Galaxy was labeled in a star chart that was in Captain James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, okudagram)
The Lactrans had a history spanning back more then tens of thousands of their own centuries.
The Starfleet survey ship USS Ariel was the first to explore the planet in 2269, and no information was available about it prior to its mission. However, the Ariel away team disappeared, and the rest of the crew disappeared after also beaming down to search for the team.
Six weeks later, the USS Enterprise reached the planet to search for the Ariel crew. The crew discovered that the three members of the original away team had perished, and the rest had been imprisoned.
Sensors later revealed a large concentration of lifeforms 98.5 kilometers northeast of the desert portion of what turned out to be a zoo.