Eren Yıldız
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If you're into history, this is a must visit on Baku. They have partial payment for the sections in the complex. If you visit the main complex (which I believe is enough for a regular tourist) you pay around 15 manat as a foreign, which is OK. Inside you'll find tombs, court, mosque, yard and pretty much a palace complex overall. There also souvenir shops inside, though items were a bit overpriced.
I only reduce 1 star because the information on the labels wasn't enough in my opinion. I'm not sure if it was done intentionally (so that you hire a guide?) or not, but it was very brief what you read about a structure.