Salt
All through history the availability of salt has been pivotal to civilization. Humans have always tended to build communities either around sources of salt, or where they can trade for it.

In Britain, the suffix "-wich" in a placename means it was once a source of salt, as in Sandwich and Norwich.

The Natron Valley was a key region that supported the Egyptian Empire to its north, because it supplied it with a kind of salt that came to be called by its name, natron.

What is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC.

Even the name Solnisata means "salt works".

Salt production
Salt production in Halle, Saxony-Anhalt (1670)
Salt was of high value to the Hebrews, Greeks, the Chinese, Hittites and other peoples of antiquity. Aside from being a contributing factor in the development of civilization, salt was also used in the military practice of salting the earth by various peoples, beginning with the Assyrians.

In the early years of the Roman Republic, with the growth of the city of Rome, roads were built to make transportation of salt to the capital city easier. An example was the Via Salaria (originally a Sabine trail), leading from Rome to the Adriatic Sea.

Salt ponds
Ponds near Maras, Peru, fed from a mineral spring and used for salt production since the time of the Incas.
The Adriatic, having a higher salinity due to its shallow depth, had more productive solar ponds compared with those of the Tyrrhenian Sea, much closer to Rome.

Red salt
Red rock salt from the Khewra Salt Mine in Pakistan
The word "salary" comes from the Latin word for salt because the Roman Legions were sometimes paid in salt. They say the soldiers who did their job well were "worth their salt."

During the late Roman Empire and throughout the Middle Ages salt was a precious commodity carried along the salt roads into the heartland of the Germanic tribes.Caravans consisting of as many as forty thousand camels traversed four hundred miles of the Sahara bearing salt to inland markets in the Sahel, sometimes trading salt for slaves: Timbuktu was a huge salt and slave market.