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The Cadmea, or Cadmeia (Greek: Καδμεία), was the citadel of ancient Thebes, Greece, named after the legendary founder of Thebes, Cadmus. The area is thought to have been settled since at least the early Bronze Age, although the history of settlement can only be reliably dated from the late Mycenaean period (c. 1400 BC onwards).
Classical period 
In the Classical and early Hellenistic periods, the Cadmea served a similar purpose to the Acropolis of Athens; many public buildings were situated there, and the assemblies of Thebes and the Boeotian Confederacy are thought to have met there. During the Spartan (382-379/2 BC) and Macedonian occupations of Thebes, the foreign garrisons were stationed on the Cadmea.
Destruction and rebuilding 
The Cadmea was destroyed by Alexander the Great in 335, who razed the city of Thebes as a warning to other Greek cities contemplating revolt against his rule. Cassander, the Macedonian general who inherited the Greek territorial possessions of Alexander the Great after his death, rebuilt the Cadmea in 316 BC.
Different meaning of cadmea 
Cadmea is also an ancient name for calamine or zinc carbonate. Combined with copper it was used in ancient (Roman) times for the production of brass (copper-zinc alloy), as mentioned for instance by the Roman author Plinius (Pliny) the elder. The element Cadmium (Cd) was isolated for the first time in 1817 from an impurity in calamine, hence the name Cadmium.