The Incans used three main type of building style. The first one is the lowest form where the stones aren't perfectly aligned and there is mortar in between the stones. The second type, the Incans used stones that fit perfectly with each other and didn't use mortar. Then the last one, called Imperial Inca is similar to the second style but the stones are roughly the same size as well. The Imperial Inca style was reserved for the most important and sacred buildlings.

What you are looking at is a ceramonial building that uses the Imperial Inca style of building, The stone slab in the middle of the building was used for sacrificing young animals. Our guide was telling us that the Spaniards who invaded the Incans mis-understood that the Incans sacrificed young animals like llamas and thought that they sacrificed young human virgins. Incans did not do human sacrifices contrary to popular beliefs. Or so says our guide.