Colombia is ethnically diverse, its people descending from the original native inhabitants, Spanish colonists, Africansoriginally brought to the country as slaves, and 20th-century immigrants from Europe and the Middle East, all contributing to a diverse cultural heritage. This has also been influenced by Colombia's varied geography, and the imposing landscape of the country has resulted in the development of very strong regional identities. The majority of the urban centres are located in the highlands of the Andes mountains, but Colombian territory also encompasses Amazon rainforest, tropical grassland and both Caribbean and Pacific coastlines. Ecologically, Colombia is considered one of the world's 17 megadiverse countries, and of these, the most biodiverse per square kilometer. Colombia is a middle power and a regional actor with the fourth largest economy in Latin America, is part of the CIVETS group of six leading emerging markets and is an accessing member to the OECD. Colombia has a diversified economy with macroeconomic stability and favorable growth prospects in the long run.