Quick answer: Three days around Cusco means an acclimatisation day, the Sacred Valley, and Machu Picchu — at altitude, so pace day one.
Cusco sits at 3,400m, so this plan eases you in before the big sights. Build in extra days if you want to trek.
The itinerary, day by day
Day 1 — Acclimatise in Cusco
Take it easy: the Plaza de Armas, the Cathedral, Qorikancha and the artsy San Blas district. Drink coca tea and rest for the altitude.
Day 2 — The Sacred Valley
Tour Pisac’s ruins and market, the fortress at Ollantaytambo, and the terraces of Moray and the Maras salt pans.
Day 3 — Machu Picchu
Take the train from Ollantaytambo to Aguas Calientes and spend the day at Machu Picchu — book tickets and a guide well in advance.
Where to stay & when to go
Sleep in the Sacred Valley (lower altitude) if you’re struggling. Stay central in Cusco near the Plaza de Armas. The dry season (May–September) is best; add days for the Inca Trail or Salkantay trek.