Every place has its hidden treasures. I don’t know if I had been living under a rock, but as a European myself (who has admittedly never been to Poland) I had no idea that there was a salt mine in Poland, which features underground lakes, 2,000 chambers, and chapels equipped with enormous chandeliers. And yes everything is made of salt. I have no idea how this works, but the salt mine is called Wieliczka and is near Krakow. Another place to my bucket list!