Several expeditions went in search of these fabulous places, but returned empty-handed, or brought less gold than they had hoped. They found other precious metals such as silver, which was particularly abundant in Potosí, in modern-day Bolivia. They discovered new routes, ocean currents, trade winds, crops, spices and other products. In the sail era knowledge of winds and currents was essential, for example, the Agulhas current long prevented Portuguese sailors from reaching India. Various places in Africa and the Americas have been named after the imagined cities made of gold, rivers of gold and precious stones.