The 3278 hectare protected Caroni Swamp has long formed a physical barrier to the city's expansion to the south, forcing urban growth relentlessly eastward at the expense of a traffic relieving ring road. This west coast mangrove area is the island's second largest wetland after the east coast Nariva Swamp which is almost twice as large. It has well over 160 species of birds, including the national bird, the scarlet ibis. It is one of the country's most popular tourist attractions with visitor facilities and regular guided boat tours.