Where was the flush toilet invented?

Flush toilets were first used in the 26th Century BC in the Indus Vally. Flush toilets were used through out the Roman Empire. In l596 Sir John Harington published a paper describing what was to become a modern system and installed one for Elizabeth the First (although she refused to use it) The flushing mechanisms have been subject to improvement ever since
England, in the reign of Queen Elizabeth I.