Frequent buses (s/2.2) go to Pisac (elev. 3011m) in about an hour. The central square was already full of merchants when we arrived in the morning. It was a Tuesday, one of the market days (also Thursday and Sunday). After dishing down a hearty chicken soup in one of the stalls, we hiked up the ruin on a hill top, in about 2 hrs (elev. 3453m, a good workout for me to acclimatize). Bought Boleto Turistico: 10 days for s/70, valid at about 10 sites around Cusco and a couple of minor museums.
The view along the trail was pleasant, across the valley of Urubamba River, and patches of terraces. Was fun to watch the town square being filled up gradually with tourist buses. The ruin itself consists of a military compound with many barracks half way up on one gentle side, a few watch towers along the ridge, a religious complex at the top (including a sun temple) with water channels. 
Pisac ruin is said to be the largest standing Inca fortress. 
Before heading back to Cusco, silly me bought an alpaca sweater at an inflated price.
