George S.
Google
The acropolis of ancient Pharrhae (which was the name of the city until about the 10th century) is a construct that was initially built in the Mycenean Era, as it is clearly referred to as one of the cities promised to Achilles in order to rejoin the War.
The benefits of the position, upon an elevated rocky formation with competent natural defenses and overlooking an irrigated fertile plain and a navigable gulf with access to port facilities and right beside a river to ensure its water supply, were quickly acknowledged and put to use. Just as the Mycenean remains have been lost beneath the overstructures, it is quite possible that a Neolithic Megaron lies even further below.
What we see today is the result of a series of reconstructions, beginning from the Byzantine era. The Franks of the 4th crusade renovated the site extensively in the 13th century. Of the many others who came to possess the castle, the Venetians were the ones to work systematically upon it. Finally, the Ottomans kept it operational until the Greek revolution in 1821, when this was the first strategic victory of the independence-thirsting revolutionaries.
Easy to visit, great for pics, and with immediate access to refreshments just a few blocks away, if the above is of little interest.