The river begins at the point where it flows out of Lake Izabal. At the entrance to the river there is a small Spanish colonial fort, the Castillo de San Felipe de Lara, built to stop pirates entering the lake from the Caribbean when this part of Central America was an important shipping staging point.
Just after the river flows from Lake Izabal it is spanned by one of the biggest bridges in Central America. On one side of the bridge is the town of Fronteras, commonly referred to by the name Río Dulce, the local center of commerce for the area. Fronteras has a local vegetable market, attracting locals from the countryside who arrive in dugout canoes. Most of these boats are powered with Japanese outboard motors but many come to market day paddling these cayucosby hand. On the other side is the town of Rellenos.
From Fronteras the river flows east for a couple of miles. In this stretch there are several marinas and resorts. The river then flows into a long narrow lake called El Golfete. This lake has an island and a large natural anchorage. A few houses and a couple of small businesses line the shore. El Golfete is about 10 miles (16 km) long and a couple of miles wide.
From El Golfete the river meanders for six miles (10 km) in a spectacular gorge. The sides of the gorge rise up to 300 feet (91 m) on either side or are covered with teak, mahogany and palms. Wild flowers bloom throughout the foliage and howler monkeys and toucans can be seen. Waterfalls flow over the lip of the gorge after rainfall.
The river enters the Caribbean Sea near the Garifuna town of Livingston
