Only 2 km south of modern and ancient Corinth stands Acrocorinth which remained in use as a fortification and refuge until the mid 1800's.
Even though modern Corinth is spread for kilometers along the banks of the Gulf of Corinth, its acropolis, Acrocorinth is impossible to miss. It dominates the surrounding area and controls access between the Peloponnese and the mainland.
There are no clearly marked road signs probably because the locals feel none are needed. And none really are. All you have to do is ignore the signs for modern Corinth and head in the direction of the summit and sooner rather than latter you'll arrive at the small museum at its base. On the way be sure and stop at the 7th C BC Sanctuary of Demeter just before.
A road climbs from the museum to the gate and small tourist pavilion. A good three hours is needed to walk the whole area but even an hour or two will be well rewarded. The view is truly stupendous and on a clear day you can see the Acropolis in Athens and the island of Aegina to the east and far across the Peloponnese where other mountain top bastions unfold before your eyes. The Gulf of Corinth is to the north and the Saronic Gulf to the west.
The hill upon which Acrocorinth rests is huge limestone butte 575 meters high. In its glory the fortress walls extended almost 3,000 meters and enclosed 240,000 sq. meters of area. The only path to the top is protected by three lines of fortification contributed to by the following.
Acrocorinth is one of the most imposing natural fortresses in Europe not only for its natural advantages of size and height but because It has a good water supply collected in cisterns. You shouldn't expect expect gleaming temples and snow white statues but do expect to work up a light to heavy sweat trudging around the vast hilltop in the sun. If you leave the well worn paths, which you will be tempted to do at many points, there are brambles and thorns to negotiate, so a pair of sensible shoes is a good idea. Keep an eye open for the elusive ancathus weed in its natural state as it was what inspired the Corinthian column. I have never seen one anywhere else for that matter. There are places where it is possible to sprain an ankle or worse so do not let your small children run around unsupervised. This is an imposing ruin and so big it is possible to get lost.
As you enter the entrance gate you'll soon pass a dry moat which used to have a drawbridge. Soon you'll come to the first of the three gateways which are connected by ramps some of which are cobbled and some dirt. The outer gate is mostly of Turkish origin while the middle is mostly Venetian built upon the ruins of the Franks.
More ancient masonry may be seen interwoven into the latter fortifications. Also to be seen are the remains of Turkish houses, Byzantine chapels and brick covered cisterns one of which covers the Upper Peirene Spring. The spring is protected by a Hellenistic well house and further covered by modern cement. The clear and cold water is not safe for drinking and is 4 meters deep and has never been known to sink lower than that level.
As you ascend to the higher of the two summits of Acrocorinth directly behind the spring you will see where at various times in the past were located a watch tower, a mosque a small church, a Venetian belvedere and the Temple of Aphrodite. Here, in all likely hood preached St. Paul. The temple was devoted to the aspect of Aphrodite worshipped in Syria as Astarte and was a center of religious prostitution. Over 1,000 prostitutes worked here and Acrocorinth was famous for its licentiousness all over the ancient world because of it. Little remains now. The next closest hill contains the tiny Frankish castle of Mont-Escoree (bare mountain).