Before the salt ponds and the Inca Trail hike and Machu Picchu, there was one more Inca ruin that we visited—Moray, an archaeological site about 30 miles northwest of Cusco. We went to Moray on the same tour that included the Maras salt ponds and I do recommend taking a tour (we booked ours through our hotel)—and a load of Dramamine if you get car sick on speeding, rickety buses like I definitely did.
Moray comprises several circular terraces and it has been speculated that they were used by the Incas to study crops. Their depth creates as much as a 27°F temperature difference between the top and bottom terraces, and you can definitely feel that difference as you descend. The largest depression is 98 feet deep, and the site also includes an irrigation system (the Incas were wizards with water flow).
We didn't have a ton of time to explore the Sacred Valley before we left for our hike but I think we definitely chose the right tour. It might be sacrilege to say so, but after a while Inca ruins all sort of start to look the same—so much so that by the time we got to Machu Picchu it felt a bit anti-climactic. Moray felt different though—the stone work and terrace layout are Inca signatures for sure, but the concentric circles are just so perfect and visually stunning. You can only walk around—not inside of—the circular terraces, making for some excellent people-less photo opportunities although it's impossible for photos to capture the immense scale of this place.
I remember being fascinated by crop circles as a kid, and annoyed when it was revealed that they were done by humans (allegedly!). But attributing things like this to aliens is actually just doing a disservice to the very real humans that created them—probably out of necessity and with slave labor, unfortunately, but also with ingenuity and an incredible eye for composition—thousands of years before the promise of Instagram likes even existed.