For those of you who don't want to check the article on this guy, he was the king of Bavaria from 1864 to 1886 and was definitely, definitely crazy. Aside from commissioning the Neuschwanstein castle (which is credited with inspiring Walt Disney to build Disney castle in that style), he had some really interesting stuff built in his Versailles-themed castle, Linderhof Palace.
Before I get to the thing I really enjoy about Linderhof, I'll quote from the Wikipedia article about one room in the castle:
Hall of MirrorsApparently this room had an ostrich plume carpet. That's class. It's also worth specifically pointing out that Ludwig used to sleep during the day and stay up all night. My kind of guy.
This room was used by the king as some kind of living room. He enjoyed sitting in the niche, sometimes reading there the whole night. Because Ludwig II used to sleep in the daytime and stay awake in the night, the mirrors created an unimaginable effect for him when they reflected the light of the candles a thousand times.
But that's not even the best part about this palace. No, the best part is the so-called Venus Grotto. What is this grotto, you ask? Well, it's a cave. An artificial cave.
You see, Ludwig II clearly spent no time ruling the country, so he had to take up his time doing something. So he commissioned an artificial cave to be built in the image of something from Richard Wagner's operas. In fact, he liked Wagner so much that he built a room in his castle to house the composer. (Wagner, apparently, was happy to accept boatloads of money from the king.)
What did he do in the cave? First, take a look at the thing. It's awesome. He listened to Wagner's operas while floating around his private bat-cave. He had a stage and an orchestra pit. He even had dynamos installed to light the cave in different colors. He had a swan boat to float around an artificial lake in an artificial cave with dynamic lighting. Might I remind you that this was the 19th century?
So, to summarize: In one of his many castles, King Ludwig II built a private underground lake/cave in which he could float around on a swan boat listening to private performances of Wagner operas.
He was obviously very rich. And if an opera cave isn't eccentric, I don't know what is.