What to expect
This is the fuller southern route: coast to Arequipa, then Colca and Lake Titicaca before Cusco. Three weeks allow more landscapes than two, but the map hides the effort between them. Nazca–Arequipa, Colca–Puno and Puno–Cusco each need a travel day of their own.
How it fits into a journey
Suggested plan: days 1–2 Lima (2 nights); day 3 Paracas (1); day 4 Huacachina (1); day 5 Nazca (1); day 6 Nazca and overnight bus to Arequipa (1 bus night); days 7–8 Arequipa (2); days 9–10 Chivay/Colca (2); day 11 travel to Puno and day 12 one selected Lake Titicaca outing (2); day 13 travel to Cusco and day 14 city (2); days 15–16 Ollantaytambo (2); day 17 Aguas Calientes (1); day 18 Machu Picchu and return to Cusco, days 19–20 Cusco (3); day 21 departure. Total: 20 nights. Confirm the direct Colca–Puno connection on your date before fixing the adjacent hotels.