The Silk Roads were overland routes connecting China to the Mediterranean Sea, which allowed the trading of silk, paper, gold, jewels, horses, and other goods. These began during the 2nd Century BCE at the time of the Roman Empire in the West and the Han Dynasty in the East. The Silk Roads remained active until the 15th Century CE, when they were largely replaced by maritime trading routes. At present they are mainly used for archeological research and tourism. The illustration shows a modern camel caravan in the desert near Dunhuang. As well as trade goods, the Silk Roads facilitated the movement of religious ideas. Judaism, Zoroastrianism, Buddhism, Manichaeism, Christianity, and Islam followed the Silk Roads into China. Mithraism, Manichaeism and Islam spread into Europe.