This remarkable feature of Portugal's west coast at the mouths of the River Vouga and the River Antuã is a vast lagoon, criss-crossed by navigable channels, dotted with islands and bordered by salt marshes and pine trees. The Aveiro is rich in fish, and seaweed (molico) used as fertilizer. In summer, boat trips allow visitors to explore the lagoon: salt-gatherers' boats, fishermen's and peasants' craft, and seaweed-gatherers' moliceiros.