The Peloponnese misses being an island by only six km, the width of the Isthmus of Corinth, connecting it to the rest of mainland Greece. Cut through the solid rock of the isthmus is the Corinth Canal. Constructed in the 19th century, it links the Ionian and the Aegean seas. It has a depth of 8m and a surface width of 24m. The waters travel to speeds of up to 3 miles per hour, changing direction every 6 hours (when it does so the current comes to a stand still). With vertical sides rising 90m above the water, it is an impressive sight. Archaic ruins and medieval monuments are more abundant here than anywhere else in the country: Venetian and Frankish fortresses, Byzantine cities and ancient Greek sites. It's a location of phenomenal and diverse beauty with towering snow-capped mountains, orchards and river valleys, fine beaches, and near desert.