The first site I visited was the Cathedral, which lies on one side of Plaza de Armas. It is huge and majestic. It has two beautiful chapels on its sides with gold and silver covered altars. The main building was being restored, yet I got an eerie reminder of the Cathedrals in Spain (specially the one in Madrid) when I got a peak of its interior. It makes sense of course since the Spaniards built it :).
The Cusco Cathedral was built in 1550 in the Baroque Style, right on the foundations of the palace of Inca Wirachocha. A really nice place to visit in Cuzco and its located in the Plaza Mayor.