The Tomb of the Mother of God is located in Gethsemane in the Holy Land. We have no relics of the Theotokos’ body because, three days after her death, her falling asleep (as death is understood in the language of the Church), she was bodily resurrected and taken into heaven, experiencing what all the Saints and faithful will encounter at the Second Coming of Christ with the general Resurrection of the dead. Thus, her body and soul were united together again.
The following is an excerpt from the book A Pilgrim’s Guide to the Holy Land For Orthodox Christians by Holy Nativity Convent, St Nectarios Press: Seattle, Washington, 1997.
Tradition tells us that at the time of the Dormition of the Mother of God, she was carried in procession and laid in a tomb by the Apostles. The Apostle Thomas arrived late and requested that he might also bid her farewell. Upon opening the tomb, they found that her body was not there. A magnificent church was built over the tomb in the 5th century and destroyed in the 7th century by Chosroes the Persian; only the crypt of the church was preserved. To protect it, the Crusaders erected the existing building over the crypt. While descending the stairs into the crypt, one passes the tombs of Sts. Joachim and Anna on the right, and on the left, the tomb of St. Joseph the Betrothed. Being so far below street level, the crypt occasionally floods during the rainy season. The marble covering of the tomb was removed recently because of extensive water damage; it was then discovered that most of the original tomb was still intact. Christian chroniclers state that the tomb of the Mother of God had been taken to Constantinople, but to the joy of the faithful, only approximately a third of it had been removed. The remainder was encased in plexiglass.