Nyasaland

Nyasaland was an African country to which the Fourth Doctor, Harry and Sarah Jane once travelled. While there, they got embroiled in a hunt for a mythical beast called a "Nandi Bear". In the process, they convinced the tribal chief to deceive the tribal shaman about the success of the hunt. Though this deception was beneficial in the short run, the shaman eventually discovered he'd been duped. The chief was then executed, and the tribe failed to progress as swiftly as it might have. (ST: To Kill a Nandi Bear)

Nyasaland thus joined the ranks of places like the Ark and the Game Station where the Doctor's well-intentioned influence was almost certainly deleterious.

Behind the scenes
Nyasaland's modern name is Malawi.