cusco is a city in southeastern peru, near the huatanay valley (sacred valley) in the andes mountain range. it is the capital of cusco region. the city has a population of about 300 000, triple the population it contained just 20 years ago. alternate spellings include qusqu (in old quechua), cusco, (after the spanish arrived), and current quechua. cusco is the preferred way to spell it in spanish.