Glimpses of San Lorenzo are first given in the episode "Parents Day", albeit the country is not named until "The Journal", in which Arnold finds his father's journal and reads about his adventures in the country. At the end of that episode, Arnold finds a map of the region in San Lorenzo where his parents went before they disappeared. The main events of Hey Arnold! The Jungle Movie takes place in this country.
San Lorenzo is a fictional country, located between Guatemala and Belize. To the north and east, the country has an airport and a single major city called Puerto Clara, where most of the citizens live (including Eduardo). Some farming lands, marshes and a river called Río Velasco are visible more to the south.
The vast majority of San Lorenzo is covered by jungles. A large river called Río Claro starts at the coastline and goes right through the country, at one point deviating into the Río de Oscuridad, which is much more hazardous and filled with rapids. Among other topographic details are several waterfalls, and at least one active volcano called Volcán Terrible. There are also remains of numerous architectural structures built by the Mayans, among other civilizations. A rainforest preserve is at the center of the country, and to the west of it is unknown territory.
San Lorenzo is also home to a mysterious group of people known as the Green Eyes, who are said to be the country’s original inhabitants, and speak an unknown, presumably native, language. The Green-Eyed People have an advanced city hidden in the unknown area of the country, seemingly in some sort of crater, or a dormant volcano caldera.
Other ethnic groups include Mestizos and Amerindians, who speak Latin Spanish. The notorious river pirate Lasombra has a presence in the deeper parts of the country. Besides having human inhabitants, San Lorenzo also hosts a wide variety of jungle animals, including butterflies, snakes, jaguars, monkeys, and wild boars, to name just a few species. In addition, Abner was most likely born in San Lorenzo, as he was a wedding present to Miles and Stella from the Green Eyes.
- San Lorenzo is also the name of an insular nation described in Kurt Vonnegut's book Cat's Cradle.
- Craig Bartlett confirmed in his second interview on The Arun Mehta Show that his use of the name is, in fact, intentional.