There's been so many times I've visited a friends palace but not known how to ask this.
English is not my native language, and I was wondering, wouldn't it be "contains" in this case.
I'm a native english speaker, and sadly the answer is no. "Does the palace contains a courtyard?" sounds strange to me. I have no idea why it's wrong, but sadly it is.
Verbs take an -s ending in third person, but only once. In a question, 'does' already has the ending, therefore it is not added to 'contain'. This is why 'contains' is wrong here.
Could it be simply Does this palace have a courtyard?
In regards to meaning, yes, it would be more or less the same thing. However, since Duolingo usually wants a pretty direct translation when possible, we need 'contain' for 'enhavas', instead of 'have' which would be 'havas' in Esperanto.
Do, kiel oni diras "court", se "korto" signifas "courtyard"?
A law court is "kortumo" or "tribunalo" and a royal court is (I think) "kortego".
Kia palaco ne enhavas korton?!
Try saying "Ĉu ĉi tiu" twice as fast!
Not yet, as you just mentioned! But still, an interesting feature for a memory palace. I'll consider adding one.