At NAOJ in Mitaka, excavation of an ancient tomb has been underway since 2005. On September 8, the tomb was open to NAOJ staff for the first time, following the opening to the public on September 6 and 7. This is a very rare key-shaped tomb, which was acknowledged as the fourth found in Japan. In the burial chamber, some burial goods have been found such as a pottery pot, from which the tomb is estimated to have been constructed in the middle of the 7th century. The picture shows the entrance of the tomb. This day, participants were allowed to go up on the tomb and look around the stone chamber.