The correct answer is - lost city of the Incas.
Machu Picchu is one of the many cities that the Incas built, but this city is something special. It is built very high in the Andes, on a place where even nowadays it will be incredibly difficult to manage to build a city, it is built beautifully, well designed, and with astonishing precision and skill. This city is the biggest tourist attraction in the country of Peru, and it is one of the ''world wonders'' that fascinates people from all over the globe.