The Lower Courtyard of Kaer Morhen in The Witcher 3: Wild Hunt.
Seen in the Tutorial Quest.
Geralt races Ciri here from the Battlements
Here is where Witchers do a lot of their combat training
There is a Training Dummy here to help with the training.
Towards the end of the Tutorial Quest, Geralt, Vesemir, Ciri. Eskel, and Lambert are all here to practice combat.