Planetario Cuzco

The closest and largest of these ruins is the amazing Sacsayhuamán (sometimes called Saqsaywaman and pronounced "Sock-say-wah-mun"), the ruins of an Inca fortress high above Cuzco. It is a steep climb from the Plaza de Armas up Plateros street which changes to Saphi. Look for the long staircase on the right, follow the paved curvy road up to the next cobblestone pedestrian path and follow this climb past the first closed control point to the second control. No need to take a cab if you can handle it. But, be careful, as robberies have been reported in mornings and evenings. There is a charge to explore the ruins at the second control or present your boleto turistico. Those on a budget can get a sense of the ruins without paying by walking up the hill and up to the entrance. You can then walk to the adjacent hill with the big Jesus on it and look down on the city. The sheer size of the stones that were moved and the importance of the battle there make it worth entrance fee. Even though only 20% of the fortress remains, the ruins are huge—budget at least two hours for exploring them. They include a dark tunnel you can walk through and a sloped rock that kids love to use as a slide. Read up on the battle beforehand as the guides don't discuss it. Also, a view of the circular base of the former tower as shown in many of the photos is not possible due to the protective ropes. Go earlier in the morning as later visits are disrupted a bit by whistles from guards telling unobservant tourists to get off the ruins. Or go even more early (before 07:00) and get in for free (2013).

In the Municipal Palace at Plaza Regocijo, this museum has exhibitions of contemporary art. Admission with the boleto turistico

A shop ("museum") explaining the history of cacao (free) and offering chocolate workshops (not free) as well as cacao farm tours (not free). Different recipes from around the world are available all made with chocolate from the factory inside the cacao and chocolate museum. Great artisanal and organically sourced hot chocolate.

Extensive museum of pre-Inca, Inca, and colonial artifacts. Labels in English and Spanish, though the descriptions in English are sometimes pretty different from the ones in Spanish.

In the home of the Inca historian Garcilaso de la Vega, this 2-story museum has many paintings from the 17th and 18th century as well as historical displays chronicling the pre-Hispanic Inca civilization, the invasion of the Spanish and the role of Christianity in the post-conquest era. A tour is unlikely to take much more than an hour.

The park square has churches, shops, restaurants and bars surrounding it, and is a great place to spend an afternoon. The historical center of Cuzco is beautiful, but you will have to deal with all the street vendors and hawkers of cheap paintings and other souvenirs. They are everywhere in and around the Plaza de Armas. They somewhat spoil the experience.