A central plot device in InuYasha, the Bone Eater's Well is a dry well so named because the bones of dead demons (yōkai) were traditionally disposed of by being thrown into it.
Either Kagome Higurashi or InuYasha or both together can travel between modern time and the Sengoku period of feudal Japan (circa 1500 AD) by descending to the bottom of the Bone Eater's well and then climbing out of it. They can carry objects with them.
As of Chapter 553, the well has vanished from both the past and present, much to the surprise of Sota and Grandpa; however, Kagome is rendered invisible whenever she stood in the area where the well once stood, suggesting its presence has not been completely eradicated. By the final chapter, the well has reappeared in both the past and present, but appears to have shut down its time travel function for three years, until the day Kagome graduated from high school. This may indicate that it was Kagome's own subconscious desires that shut it down. After her graduation, it reopened and allowed her to rejoin Inuyasha, and possibly will allow her to go back to visit her family occasionally.
Location
In modern time, the well is enclosed by a building within the Higurashi family shrine. In the Sengoku period, it stands alone in the forest near Kaede's village.
Appearances
The first occasion when the well was used for time travel was when Kagome was dragged into it by Mistress Centipede. It had been sealed shut, but Mistress Centipede broke through the seals to try to get to the Jewel of Four Souls which was inside Kagome's body.
Subject: Bone Eater's Well 
Fri Aug 28, 2009 6:14 am