was discovered, the Horn was believed to be the southernmost point of Tierra del Fuego; the unpredictable violence of weather and sea conditions in the Drake Passage made exploration difficult, and it was only in 1624 that the Horn was discovered to be an island. It is an interesting testament to the difficulty of conditions there that Antarctica, only 650 kilometres (400 mi) away across the Drake Passage, was discovered as recently as 1820, despite the passage having been used as a major shipping route for 200 years. The clipper route fell into commercial disuse with the introduction of steam ships, and the opening of the Suez and Panama Canals. End of exploration The age of exploration is generally said to have ended in the early 17th century. By this time European vessels were well enough built and their navigators competent enough to travel to virtually anywhere on the planet. Exploration, of course, continued. The Arctic and Antarctic seas were not explored until the 19th century. Age of Sail The Age of Sail originates from ancient seafaring exploration, during the rise of ancient civilizations. Including Mesopotamia, the Far East and the Cradle of Civilization, the Arabian Sea has been an important marine trade route since the era of the coastal sailing vessels from possibly as early as the third millennium BC, certainly the late second millennium BC up to and including the later days of Age of Sail. By the time of Julius Caesar, several well-established combined land-sea trade routes depended upon water transport through the Sea around the rough inland terrain features to its north. These routes usually began in the Far East with transshipment via historic Bharuch (Bharakuccha), traversed past the inhospitable coast of today's Iran then split around Hadhramaut into two streams north into the Gulf of Aden and thence into the Levant, or south into Alexandria via Red Sea ports such as Axum. Each major route involved transhipping to pack animal caravans, travel through desert country and risk of bandits and extortionate tolls by local potentiates. Southern coastal route past the rough country in the southern Arabian peninsula (Yemen and Oman today) was significant, and the Egyptian Pharaohs built several shallow canals to service the trade, one more or less along the route of today's Suez canal, and another from the Red Sea to the Nile River, both shallow works that were swallowed up by huge