Built somewhere between the 13th and late 15th century, this Irish castle has seen more gruesome deaths than a Game of Thrones wedding. As legend has it, during a struggle for power within the O’Carroll clan (which had a fondness for poisoning dinner guests), one brother plunged a sword into another, a priest, as he was holding mass in the castle’s chapel. The room is now called “The Bloody Chapel,” and the priest is said to haunt the church at night. And the horror doesn’t end there. During castle renovations in the early 1900s, workmen found a secret dungeon in the Bloody Chapel with so many human skeletons, they filled three cartloads when hauled away. The dungeon was designed so that prisoners would fall through a trap door, have their lungs punctured by wooded spikes on the ground, and die a slow, horrific death within earshot of the sinister clan members above.