The story is set in Paris, and was the first Doctor Who serial to feature footage filmed on location in a foreign country.
The script is credited to "David Agnew", a pseudonym for Graham Williams and Douglas Adams - then respectively the producer and script editor of the series - who wrote the script themselves when a script commissioned from another writer failed to meet with their approval. Thanks the Adams' involvement, the script is full of witty dialogue and several Hitchhiker's Guide to the Galaxy references.
City of Death is considered by many Doctor Who fans to be the greatest Doctor Who serial of all time, although this is by no means universal and other fans have produced scathing reviews.