I really love buildings, especially those that are especially historical, unusual and atmospheric, and I believe The Talatal Ghar - Kareng Ghar meets all three of these quite easily. It's historical because it's over 200 year old and was a palace of the royal family. It's atmospheric due to its unusual 3 -4 structure, being half above and half underground, plus all those secret passages and tunnels add to the mysterious side of it. The unusual thing, and the trivia question from the title concerns the material it was built with, or more precisely, what was used to hold the bricks together? I won't tell you yet, as it is a fun thing to research. I will say I was shocked and impressed.