Costa Marques is a city located in the state of Rondônia, Brazil. It has a population of approximately 15,000 people. The city is situated on the Costa Marques river, near the border with Bolivia. Costa Marques is known for its natural beauty, with the river and surrounding forests offering opportunities for fishing, boating, and other outdoor activities. The city also has historical importance, as it was an important trading post during the rubber boom in the late 19th and early 20th centuries.