The name "Pearl River" comes from the pearl-colored shells that lie within the Pearl's riverbed as it flows through the city of Guangzhou. A 500 kV power line, suspended from three of the tallest pylons in the world, crosses the river near the Nansha Bridge. The mouth of the Pearl River forms a large bay in the southeast of the delta, the Pearl River Estuary, the Bocca Tigris separates Shiziyang in the north, Lingdingyang in the south, and Jiuzhouyang at the southern tip of the estuary surrounded by the Wanshan Archipelago. This bay separates Macau and Zhuhai from Hong Kong and Shenzhen.