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, 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. On the other side is Rellenos. 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 cayucos by hand.
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 and 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.
Izabal is bordered to the north by Belize, to the north east by the Gulf of Honduras, and to the east by Honduras, and by the Guatemalan departments of Petén to the north west, Alta Verapaz to the west, and Zacapa to the south.
The department of Izabal surrounds Lago Izabal (or Lago de Izabal), Guatemala’s largest lake (about 48 km long and 24 km wide, with an area of about 590 km²). The Spanish Colonial fort of San Felipe, now a Guatemalan national monument, overlooks the point where the lake flows into the Río Dulce.
The small town of Izabal is on the south shore of the lake; before the construction of the ports of Livingston and Puerto Barrios in the 19th century this was Guatemala’s main Caribbean Sea port and was the original seat of Izabal department; nowadays, however, Izabal town is a remote village that gets little traffic.
From the area around Lake Izabal, the Department of Izabal stretches along the Río Dulce to the coast of the Caribbean Sea.
The department of Izabal includes the ports of Puerto Barrios (the departmental seat), Santo Tomás de Castilla, Livingston and Guatemala’s free trade zone Zolic. Izabal also includes the Pre-Columbian Maya ruins of Quirigua.