The Peru itinerary that rarely stays on schedule
You land in Lima, intend to spend a few nights eating your way through the city, and then fly to Cusco. Once there, you discover that the Sacred Valley deserves more than a quick excursion. Maybe you add Ollantaytambo.
Peru's official tourism site places the Sacred Valley within reach of Cusco and highlights towns such as Pisac, Chinchero and Ollantaytambo. It also lists Lima–Cusco air travel at roughly an hour and fifteen minutes as a reference.
That flexibility creates one practical question before departure: what flight will you use to leave Peru if someone asks for evidence of your onward plans?
Choose the exit route before choosing a document
Consider a traveler arriving in Lima on August 6. They plan three nights in Lima, six nights around Cusco and the Sacred Valley, and several days with no firm hotel booking. Their tentative departure is August 23.
One possibility is to return to Lima and take an international flight from there. Another is to investigate a suitable international departure from another Peruvian airport, subject to actual schedules and connections. What does not work as an international exit is a reservation from Cusco back to Lima: both airports are in Peru.