Somewhere you know so well you can walk it in your mind without effort — almost always your own home.

The palace only works if the place is already rock-solid in memory, so all your effort goes into the images, not into remembering the building. Best first choices:

• Your home — the gold standard; you know every room and object.
• A childhood home, your workplace, your daily commute, a familiar shop.

Avoid places you've only seen once or invented from scratch — you'd be trying to memorise the palace and the content at the same time, which defeats the purpose.