"It's a dog park," explains the Doctor. "For dogs that live in cities to be able to run and play."
Romana looks skeptical. "You do know K9 is a robot, right?"
"Shh," says the Doctor, and points to K9 in the distance.
"Error. Error," his voice burbles faintly. "Play object now aquatically located." He circles his ears sadly towards a tennis ball bobbing in the dubious-smelling pond. "Request assistance."
An enthusiastic spaniel lollops into the water, grabs the ball in its mouth, play-bows to K9, then runs away. The little robot gives chase, beeping happily.
"See, he's made a friend!"