Archaeologists believe they have discovered the palace of Japan's "Boadicea" – the warrior Queen Himiko.
The building covering nearly 300 square metres was located close to the city of Sakurai and the former Japanese capital of Nara, 300 miles south-west of Tokyo.
Built on stilts, the structure was found beside three other aligned buildings, leading archaeologists to believe it is the site of Himiko's Yamatai palace.
"A building cluster that is placed in such a well-planned manner is unprecedented in Japan at that period in time," Hironobu Ishino, director of the Hyogo Prefectural Museum of Archaeology, told Kyodo News.
The discovery coincided with celebrations today to mark the 20th anniversary of the enthronement of the present emperor.
Queen Himiko is a popular character in Japanese history. She was apparently able to wield great power in the Yamatai Kingdom from around the end of the second century. Legends handed down from the time describe her as "being skilled with magic".
Japanese revere her as a heroic Boadicea-type figure who unified the kingdom after years of fighting with rival tribes, before her death around 248AD.
The precise location of Yamatai has been one of the most bitterly disputed issues in Japanese archaeology, with some claiming the kingdom was in present-day Kyushu. The latest finding supports the claim of central Japan to the queen's lands.
The researchers' conclusions on the palace are supported by a huge traditional keyhole-shape tomb which is nearby and may be the last resting place of the third-century relative of Emperor Akihito.
Excavation of the tomb could settle that debate once and for all, although the Imperial Household Agency appear to have ruled that out.
Security in Tokyo has been stepped up ahead of official celebrations to mark the 20th anniversary of the emperor's accession to the Chrysanthemum Throne, the longest royal dynasty in the world.
Akihito took over the throne after the death of his father, Emperor Hirohito, in 1989.
Ceremonies are to be held at the Royal National Theatre and 30,000 people are expected to attend a public ceremony later in the day.
More than 16,000 police have been mobilised to provide security and demonstrations by extreme left-wing groups opposed to the imperial system are planned just outside the grounds of the palace in central Tokyo. Clashes with nationalist groups are expected.---telegraph.co.uk