Ancient Greek inventions were new devices from around 2,500 years ago. Some of their ideas and inventions are still in use today. Did you know that the watermill was invented by Greek engineers somewhere between the 3rd and 1st century BC? Or that democracy began in ancient Athens? Or that theater has its origins in Ancient Greece? Ancient Greek customs are still with us too. The Olympics began 2,500 years ago in Ancient Olympia in Greece and it was revived as the modern Olympic Games in the 19th Century.