Puerto Limón, also sometimes just called Limón, is a city on the Caribbean coast of Costa Rica. As is often the case in Costa Rica, "Limón" refers to both a province, canton and district, as well as a general place that we would call a "city". Here, I am talking about, more or less, the city.
The city has around 75,000 people (the canton has 95,000 apparently, but some of those live outside of the city), which makes it a fairly small city, although it is large by Caribbean standards. The city is only about 75 linear miles east of San Jose, but since getting there requires crossing Costa Rica's rugged continental divide, it takes between two or three hours to get there from Costa Rica's population center in the central valley.
The main development of Puerto Limón occurred in the late 1800s as a terminus for a rail line to help in exporting fruit (mostly bananas). To this end, indentured workers were brought in from China, Italy and Jamaica to build the railroad, and after its completion, many of those workers or their descendants stayed to work on the massive banana plantations. The Afro-Caribbean population was not granted full citizenship, and until 1949, were not allowed to leave Limón without permission. To this day, Limón has a substantially different demographic and culture than most of Costa Rica, with a sizable population of Afro-Caribbeans, many of whom continue to speak English, as well as follow other Afro-Caribbean traditions, such as being Protestant and playing baseball. In general, it feels different from the main Central Valley region of Costa Rica.
The economy is still based on fruit exporting, and massive banana plantations still fill the plains outside of Puerto Limón. In addition, tourism is an obviously important part of the economy, including both domestic tourism, and international tourism (the city having a dock for cruise ships and an international airport. Puerto Limón, and Limón province, are both less economically developed than the rest of Costa Rica, but are also still far ahead of most other countries in Central America. Also, despite its small size, Puerto Limón is not only the largest city on Costa Rica's Caribbean coast, but is actually the largest city for hundreds of miles, between Colon, Panama and La Ceiba, Honduras.
There are a lot of beautiful places to visit in Costa Rica, but Puerto Limón, with its unique culture and miles of sunny, sandy beaches, is a place that should be somewhere on the list. While not as obviously touristical as other places in Costa Rica, there are many things of interest to see there!