I’ve been up to my neck in recent weeks researching ancient isthmi. I continue to plow forward in writing a history of the Isthmus of Corinth in the Roman era, or, rather, a history of the connectivity of this Isthmus. The Corinthian Isthmus was not only the most famous isthmus of classical antiquity but also became a type of isthmuses in general. Most references to isthmuses are references to the land bridge of Corinth.
Today an elementary kid might learn in a geography class, or through a Google search, or by a Wikipedia article, that an isthmus is “a narrow strip of land connecting two larger land areas, usually with water on either side.” But an isthmos, as Greek writers originally used the term, packed greater punch. The word isthmos denoted first and foremost a very narrow neck of land formed by dramatic constriction of parallel coastlines, but, equally important to the concept was its consequential effects on mobility and movement. For historians of the Classical age, the effects of constriction on movement made an isthmus a term of power and control.
I wanted to see what the Isthmus of Corinth had in common with the other land forms identified as isthmuses from the archaic-early Hellenistic age and so I spent some time last month zooming (via Google Earth) around the Mediterranean and Black Sea, looking at landforms identified as isthmuses. More images forthcoming via this website, but for now, here is how the Isthmus of Corinth appears in Google earth from Acrocorinth.
I will also contribute now these thirteen ancient isthmuses to the list of isthmuses in Wikipedia. Nota bene: this list is not (of course) the sum total of all isthmi of the ancient Mediterranean, but rather, necks of land identified as isthmuses in literature of the Classical and early Hellenistic periods.
1. The Isthmus of Corinth (Corinthia, Greece)
2. The Isthmus of Cnidus (Datça Peninsula, Turkey)
3. The Isthmus of
4. The Isthmus of the
5. The Isthmus of
6. The Isthmus of
7. The Isthmus of
8. The Isthmus of
9. The Isthmus of
11. The Isthmus of
12. The Isthmus of
13. The
Corinthian Matters 
Thanks for your useful post. It would be great to have your help editing these features in Pleiades (pleiades.stoa.org
Great idea, and thanks for the suggestion. I’ll do that.