used to, it was said to be the tears of Oshizu."

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Which castles is considered the most famous?

The bright white Himeji castle dates to Japan's feudal period. David Green

"Himeji castle is the most famous castle in Japan today. It is the largest original extant castle with enormous grounds, a huge tenshu (the main tower) and a number of original outer structures and gates," says Mitchelhill.

"It is beautiful, imposing and easily accessible by train from Osaka and Kyoto (in the Hyōgo Prefecture)."

And an overlooked gem you'd recommend?

"Kochi castle is one of a number of excellent castles on the island of Shikoku (southwest of Kyoto) that are worth visiting along with Marugame, Iyo-Matsuyama and Uwajima castles," says Mitchelhill.

"These castles make upfour of the 12 remaining castles in Japan with an original tenshu.

"Kochi castle has a number of interesting features: The arrangement of buildings within the innermost enclosure is unique, with the lord's reception rooms adjacent to the main tower. These buildings were usually located in a lower or outer compound.

"Slatted windows in the low mud-plastered walls surrounding the inner compound enabled samurai to keep watch; iron spikes line the top of the stone base of the tenshu to deter would-be invaders; and a 'trick gate' was used to trap an invading army."

Which is the most remote?

Hagi is one of Japan's most remote castles. David Green

"Hagi castle, on the southwest coast of Japan, is one of the more remote castles."

"It is not well known, and difficult to get to