precipitous

Crossing over onto Middle Meadow Walk after taking younger lad to an appointment at the Sick Kids, he let me rest the camera on his woolly-hatted head to take this. It was interesting how just a small increase in the zoom made the north end of the Walk look so much steeper.

It can't be as gravity-defying as it looks because I have cycled up it.
What's the optic science behind this effect?