Cuzco itself has many attractions but the surrounding are fabulous as well and you really should try to explore them.
First of all you have to be ready, that means you are not overtired and had rested at least one day in Cuzco. The altitude of some places (as the sacred valley) as lower than in Cusco, but you will have to get there you will reach the altitude of 3700 in Chinchero.
Depending from how many day you may spend in this area, your will make your selections.
For simplifying the excursion I would divide this into 3 excursions:
Near Cuzco (also called City Tour):
A half day tour with the archeological places of Qoricancha (Temple of the Sun), Sacsayhuamán (the closest and largest of these ruins is the amazing Inca), Tambomachay (a water temple conveying Inca principles of duality and displaying their mastery of hydraulics), Puca Pucara, Q’enqo (a temple dedicated to sacrifices).
Try to take a tour that starts early I the morning. You will have the change to see Pisac market and the ruins, after a lunch in Urubamba you will visit the archeological site of Ollantaytambo. (Some people stop here in order to continue their trip to Agua Calientes and Macchu Picchu). Traveling back to Cuzco depending on the time you will stop in Chinchero (archeological site).
Both Moray (agricultural laboratory of the Incas) and Maras (salt mines) are located in the mountains on the way to the Sacred Valley. You want to explore this places without a tour you may take a bus to reach the junction and negotiate a price for the tour of both places. This was our morning and early afternoon program. For the lunch we took a minibus to Urubamba we visited the marked and finally a bus brought us back to Cuzco.
Maras and Moray: