city, Osaka fu (urban prefecture), Honshu, Japan, on Osaka Bay. Many large earthen tomb mounds in the area attest to the city's antiquity. The mausoleum of the emperor Nintoku-1,594 feet (486 m) long and 115 feet (35 m) high-is the largest in Japan. Sakai was a leading seaport and commercial centre from the mid-14th to the mid-17th century. Its rich merchants traded with China, Korea, the Ryukyu Islands, and Europe. Its importance waned, however, after the institution of the national seclusion policy in 1639 and a shift in the course of the Yamato River, which silted its harbour, early in the 18th century. The city sank into obscurity as Osaka rose to commercial and industrial greatness.
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