There are many castles and palaces in the Empire that have strange architectural details, particularly in the Mantis and Unicorn clans, but none that are more strange in appearance than the complete oddity that is Kyuden Kasuga. The castle is deliberately built to resemble a tortoise shell, making it perhaps the strangest-looking building in all of Rokugan.
The formal estate of the Tortoise Clan is constructed on the peninsula leading into the bay of Otosan Uchi, for centuries the Imperial City and largest city in the Empire of Rokugan. The Tortoise used the Imperial city as their base of operations since their clan was created, and have never controlled significant holdings outside of its boundaries. Kyuden Kasuga was created only after the Tortoise were finally awarded a formal family name.