In Japan, around mid-august is know as the Obon Holiday. This is a time when you visit your ancestors and they visit you. At one point during the holiday, you are suppose to visit the graves of your ancestors - this is ohaka mairi (Ohaka means grave, and mairi means to visit). This is a part of the Buddhist (well Japanese Buddhist) religion. And it is basically to clean the grave and pay respects to your family. The grave that my family goes to is for my Japanese Grandfather.