Lost Temple

The Temple is a building under the sea that was made long ago before chakra was discovered, and was buried under the seabed in the middle of the ocean. Aoi Uchiha stumbled upon this temple when he retrieved the scroll that was used to keep the temple underground.

History
The Lost Temple was a temple where priest and other people came to, to worship these massive beast called Kaiju or monsters. These priest and people worshiped these beast because they felt that one day they would rise and cause destruction to the whole world. So by worshiping them, the priest felt that the Kaiju would spar their lives and the other people who came to worship as well. This practice went on for many years until one day, these Kaiju did come. This was hundreds of years after chakra was discovered, and the land that the Lost Temple was on was the Land of Water.

These beast came, but they weren't what the people expected. They came but they were the size of a whale, they thought that the what they worshiped was all just a lie, so they abandoned the temple and stopped worshiping those beast. But one person kept on worshiping these beast, he stayed in the temple and even had chakra and some techniques and other special things. Some things this person noticed was that the beast were only Water type monsters, they didn't come on land, and they hardly ever came up to the surface of the ocean. Upon further inspection, he found out that there were only 4 of them left from the time they came to the time now.

A few years pass and the person that stayed in the temple was loosing his spirit to worship the beast, one day he went to sleep and had a prophecy, from that prophecy he started to create things for the future for that one person who was able to control the Kaiju Then on the day he was about to stop, all the Kaiju came and attacked the Land of Water. They were huge, the size of a Tailed Beast and even larger for one of them. They were very hard to take out, weapons and jutsu didn't work, they even evolved to be on land but could only stay on land for 10 minutes then go back into the water. So the person that was in the temple constructed these scrolls that could seal up anything, so he used those scrolls and sealed up the beasts, but him and and temple went down in the process deep in the sea.

Over the years, after earthquakes and other things, the piece of land that temple was on drifted further and further out into the sea, deeper and deeper down until sand started to cover it and the pressure under the sea made it sink into the ground. No one found the temple because it was deep in the sea and in the middle of nowhere. So it just stayed there for hundreds and thousands of years, until Aoi Uchiha found it.