The Cardo was the main shopping street in Roman Jerusalem. An impressive stretch of it was excavated in the 1970s. The dig was guided by the sixth-century Madaba mosaic map, discovered in a church in Transjordan 1897. The Cardo is a prominent feature on the map and predicted exactly where the ancient street would be found. Today you can now walk around its original pillars and colonnades.
One can often overhear tour guides in the Old City explaining that the origin of the word cardo is the same as that of cardiology, meaning connected to the heart. This is a plausible-sounding etymology since the cardo was the heart of the city, but almost certainly a wrong one. The word cardo comes from the Latin word meaning hinge, pole, axis or juncture. (It is related to the English word "cardinal.") The Cardo was the hinge around which Roman-era Jerusalem turned.
The Cardo was part of the massive programme of building and public works with which the Romans attempted to stamp an indelibly Roman character on the city. They renamed it Aeolia Capitolina and, after the Bar Kochba revolt, forbade Jews to reside there in an effort to erase the Jewish connection to Jerusalem. They succeeded in part; the Roman street plan is still visible in the Old City, but only partially; Jerusalem is today a city with almost half a million Jews.