I visited this WHS in June 2019 and allowed 5 nights to explore the historic centre and the several sites around Cusco. It was a very welcome change from Lima even though there were many more tourists here. There are so many sites to see though and different festivals going on in June that it rarely felt crowded or congested except close to the main square.

If you intend to visit different sites around the Sacred Valley, make sure to buy the bolleto general which costs 130 soles and is valid for 10 consecutive days. It would cost way to much if you were to pay around 70 soles for each and every site. Apart from several minor monuments and museums (most interesting being the one of Qorikancha in Cusco), it will give you access to several Inca sites, namely Sacsayhuaman (best to visit before sunset), Qenqo, Puka Pukara and Tambomachay (these 4 can easily make up a worthwhile half day); Pisac and Ollantaytambo (quite a way from Cusco but a worthwhile stop on the way to/from Aguas Calientes and Machu Picchu); Moray and Chinchero (another worthwhile trip which we did on our way back from Machu Picchu and also included Maras salt pans and rural area); as well as Tipon and Pikillacta (which we combined with Rumicolca for an interesting visit of the Qhapac Nan and a combination of Wari and Inca structures).

At over 3400m above sea level, it is worth taking it easy for the first day to acclimatise. There's more than enough to visit in Cusco proper without overdoing it. Cusco was the ancient capital of Tahuantinsuyo, the centre of the Inca empire of the four suyus or provinces. Different panancas or royal lineages settled here and governed the colossal Andean empire. The OUV of this WHS mainly lies in the combination of colonial structures over Inca walls or foundations. Perhaps the best way to appreciate such a combination is by walking down Calle Loreto (photo) or Calle Hatunrumiyoc (where you can observe the famous 12-angled stone which is now part of the Archibishop's Palace wall). In both streets, the Inca walls make up at least half of the colonial building walls. The rear view of the Convent of Santo Domingo or Qorikancha clearly shows the superimposition of colonial architecture upon Inca constructions.

There are two UNESCO WHS inscription plaques, one just in front of the rear view of Qorikancha and the other bang in the middle of the Plaza de Armas. Even though not part of the WHS, make sure to visit Sacsayhuaman before sunset as it is one of the best Inca sites in Peru. As Nan says in his review, if you feel like hiking, you can continue uphill to an inscribed Inca road location of the Qhapac Nan WHS even though there isn't much to see there apart from the official information board.