Where is the lady of the lake?

the lady of the lake is supposedly the one who gave arthur excalibur, so where, what lake i mean, is she supposed to be found? and, what happened to excalibur after it was given back to her? my father once told me a family legend and it said that i was the descendant of arthur and remembering that i began to wonder, what happened to the sword excalibur? someone please answer all my questions!!!!