Torrid zone

The torrid zone was the name given by ancient Greek and Roman geographers to the equatorial area of the Earth, so hot that it was impenetrable.

He thought, however, that the excessive heat in the torrid zone would prevent the exploration.

And when you have proceeded about three thousand stadia in a straight line south of Meroë, the country is no longer inhabitable on account of the heat, and therefore the parallel though these regions, being the same as that through the Cinnamon-producing Country, must be put down as the limit and the beginning of our inhabited world on the South.

However, it would be impossible to get into contact with each other because of the unbearable heat at the equator (De orbis situ 1.4).

Many Europeans had assumed that Cape Bojador, in Western Sahara, marked the beginning of the impenetrable torrid zone until 1434, when the Portuguese sailed past the cape and reported that no torrid zone existed.