Fate/Stay Night
The hidden cavern beneath Ryudou temple is empty now, void of any shadows or death. Nonetheless, the stench of blood and the sweetness of rotting flowers still permeates the area, as though for eternities the cave would still remember the events that had occurred, even when no one else would. Drops of dew drop down from the cracked ceilings. The sound of heavy pouring rain fills the silence that lingers ominously.
In this place, Tohsaka Rin had used the Jeweled Sword of Zelretch, a weapon capable of slicing through multiple dimensions with the help of Second Magic. It was the only way to defeat the shadows that Sakura, a girl tainted by the darkness of Angra Manju, had summoned. She must have used the sword many times, within the empty dips of space, mana still lingers from the infinite number of parallel universes.
The knife had slashed into many different universes, of all types of varieties. There were universes where the Holy Grail War had simply not happened, where the cavern had no use, and even some where Rin herself was using the knife against Sakura. The remnants of these slashes still remain, although vague and distant. They could only be seen at certain angles, glinting in the blue light.
It's not likely at all, but theoretically one could fall into one of these universes, if done at the right angles…