Byzantine foreign trade reached out all over the world. The Byzantines imported animal skins, slaves, and sometimes wheat from Russia; precious stones from India; spices from Ceylon; embroidered rugs from Spain and Morocco; ores and wrought metals from Italy and Germany; wool and woolen goods from the Low Countries and England; hemp, flax, and amber from the Balkans and the north. These were only a few things they imported. Some of these things were shipped out again; for instance, they shipped amber from the Baltic to the Far East. The Byzantines even penetrated darkest Africa. Not only did they do business with the Ethiopian kingdom of Axum on the Red Sea where the temperature sometimes went up to 120°, but they may even have gone with the dark-skinned Axumite merchants to the mysterious city of Zambabwe. There, in the heart of the jungle, Negro tribesmen built towers, walls, and palaces so mighty that even today men look at the ruins and wonder how they did it. Gold seemed to be as plentiful as pebbles in Zambabwe, and you traded with the natives in the following way: You built a thick thorn breastwork, and on it you placed salt, iron, and the carcasses of cattle. Then you went away, and the natives slipped out of the forest and placed beans of gold upon each object. Later on you came back and if you thought they had left enough, you took the gold and the natives carried off the meat and salt and iron. If not, you moved away and the natives were given a chance to leave more gold. Sometimes this bartering went on for four or five days. Neither side saw, or even talked to, the other. The Byzantines were able to carry on this world business, because their principal city, Constantinople, had one of the most strategic locations in the known world of that time. It was like a spider in the center of a spider web; practically every trade route in the world passed through it. The Byzantines also had a large number of unusually fine seaports in other parts of the empire. Besides Constantinople itself, there was Smyrna, Thessalonica, Patras, and in the early days, Alexandria. There were several others, many of which are very good seaports even today. The Byzantines also knew how to promote business. We are apt to think of a world’s fair as something modern, but the Byzantines knew all about them. Every year, in October, they held an enormous trade fair on the Vardar plain outside Thessalonica. There they built a huge temporary wood-and-canvas city of booths and bazaars, and even amid the troubled Middle Ages, merchants and peddlers flocked to it from all over. It was only later, when the Byzantines became proud and haughty, refusing to seek business while they sat on their doorsteps waiting for business to come to them, that they got into trouble. Then the energetic Venetians, Genoese, and Pisans took over.