A large lake figures in today's Geo Quiz. The largest lake in the world is ironically the Caspian Sea; the deepest is Lake Baikal in Russia.

But we're looking for the largest freshwater lake in Japan. It's located northeast of the city of Kyoto. Shows up in Japanese literature and poetry and it shows up in the news today.

The lake was infested with bluegill fish. These fish were raised and cultivated since the 1960's as a possible protein source. They've turned into an ecological nuisance. They multiplied so much, the bluegills were wiping out local native fish species.

Bluegill Fish

They even took over the royal moat that surrounds Japan's Imperial Palace. Japan's Emperor Akihito is taking the blame for all this.

We'll explain why....when we reveal the answer...