Mauritania is known as a politically unstable country. The country has seen several coups over the years. The population often lives below the poverty line and slavery was only abolished in 1981. The population is known for being very hospitable. The country consists largely of desert plains with some small villages, towns and camels. Worth seeing in Mauritania is the Richat structure, this is a natural phenomenon whose origin is unknown. It is recognizable by the large circular shape that consists of several layers of stone. The port city of Nouadhibou is known for the many shipwrecks floating off the coast. In addition, the country is known for the longest train in the world, which runs between Zouerate and Nouadhibou over a distance of 700 km.