"Gotterdammerung" is the last in Richard Wagner's cycle of four operas titled "Der Ring des Nibelungen" ("The Ring of the Nibelung").
The title is a translation into German of the old norse phrase "Ragnarok", which in Norse mythology refers to a prophesied war among various beings and gods that ultimately results in the burning, immersion in water, and renewal of the world. I find this music very soothing for my nerves.
Yes, my friend:-) I have seen this opera performed live and it was a great experience. Whenever I hear this music I get a doomsday feeling and it soothes me. Especially at the end of this clip I always imagine walking into a forest a sunny summer day right after heavy rain, and I follow the rainbow. But it doesn't lead me to a gold treasure, but rather to my own death, which is infinitely better.