On this voyage, he circumnavigated and visited a considerable part of modern-day Great Britain and Ireland. He was the first known scientific visitor to see and describe the Arctic, polar ice, and the Celtic and Germanic tribes. He is also the first person on record to describe the midnight sun. The theoretical existence of some Northern phenomena that he described, such as a frigid zone, and temperate zones where the nights are very short in summer and the sun does not set at the summer solstice, was already known. Similarly, reports of a country of perpetual snow and darkness (the country of the Hyperboreans) had reached the Mediterranean some centuries before.