25 Best Easter Eggs & References In The MCU So Far

10. The World Tree (Captain America: The First Avenger)

When Johann Schmidt was searching for the powerful Tesseract Infinity Stone - which he described as "the jewel of Odin's treasure room" - at the beginning of Captain America: The First Avenger, the Asgardian origins of the item were hinted at by the wall that it was hiding behind. On the wall - which was in a church in Tønsberg, Norway - was a mural depiction of the World Tree. The World Tree acts as a means to travel to and between the different nine realms, one of which is Asgard and one of which is Midgard (another name for Earth). It was one of the first real Earth-based hints that other realms were part of Earth's history and, in a way, helped to pave the way for the massive expanded universe we have now accepted in the franchise.