The Sun Shrine (also known as Sun Keep in the SNES/PS version) (大陽神殿 Taiyō Shinden "Great Sun Temple") is a location in Chrono Trigger that appears in all time eras. The Sun Temple plays a role during an optional part of the game. If the heroes acquire the Moon Stone, it can be recharged here.
The Sun Temple is a small cave located on the North-eastern section of all maps. Inside, there is a small set of stairs leading to a pedestal bathed in light. The interior indicates there is a small hole that allows sunlight inside.
After acquiring the Moon Stone, it recharges by leaving it in the Sun Keep from 65000000 BC until 2300 AD. A problem occurs in 1000 A.D.; someone steals the stone, namely the Mayor of Porre, and he refuses to relinquish the stone. Traveling back to 600 A.D. and speaking to his ancestor remedies the problem. Give her Spiced Jerky for free and she ensures her children grow up generous. As a result, the Mayor in the year 1000 A.D. is happy and returns the stone.
Finally, the heroes return the Moon Stone to the Sun Keep. After traveling to the year 2300 A.D., the heroes will find the Sun Stone.
Creation and Tectonics
Many speculations exist regarding the origin of the Sun Temple. Zeal could not have created the location since it exists eons before that Kingdom's existence. Since the Sun Stone needs several millennia to charge and Zeal used Sun Stone as its primary energy source before switching to the Mammon Machine, the location existed many millions of years even before it existed in Chrono Trigger. Another point of interest is that, unlike the other continents, the Sun Temple remains relatively anchored to its geographical location; plate tectonics did not shift the island housing the location as it had other locations. The source of light in the temple is likely attributed to its global position. In the various endings of the game, a sprite of the planet is shown as being completely vertical. That means sunlight could have reached the keep consistently throughout time. This, along with the other theories, could simply be an oversight by the game designers.