Harmony was a planet which the Doctor, Ben and Polly once visited. Polly found it so idyllic she immediately named it "Heaven". The Doctor, meanwhile, dubbed it "Arcady".
It was inhabited by a near-Human species who dressed like ancient Greeks, and were dedicated to ensuring their homeworld was not misnamed. Discord was prohibited on the planet as "wasted energy". The inhabitants even spoke through music.
There were no farms or animals on the planet at the time the Doctor visited. There had been, thousands of years previously, but they had all died out. As a consequence of the extinction of most of the animal kingdom on the planet, the sentient population eventually dwindled in size to the mere 10,000 present when the Doctor arrived. What the Doctor learned was a fairly horrible secret: the planet's population was being fed by capturing and using passers-by. (DWA: Planet of Bones)