The Kostnice Sedlec, also known as the Sedlec Ossuary, is a Roman Catholic chapel located in Kutná Hora, Czech Republic. It's basically a bone-chilling (pun intended) place where the skeletons of 40,000 to 70,000 people are artistically arranged to create decorations and furnishings for the chapel. Picture chandeliers made of bones, garlands of skulls, and even a coat of arms crafted from human remains. It's like a macabre work of art that attracts over 200,000 visitors each year. So, if you're into spooky stuff or just want a unique experience, this place is definitely worth checking out!