The oldest city in Greece is Argos, which is a five-letter word. Argos is an ancient city located in the Peloponnese region of Greece and is one of the oldest continuously inhabited cities in the world. It was founded in the late Bronze Age and has been inhabited since then. The city has a long and rich history, having been ruled by many different civilizations over the centuries. It is also known for its archaeological sites, including the Temple of Hera, the Acropolis, and the Ancient Agora.