About the Șona mounds
Basically, it is not known what these pyramids in the ground, grown out of nothing on a lightly wavurit terrain. I've read from sources on the net, from an article in Adevarul, a couple of guesses.
The villagers call these mounds guruiețiwhich means earthworks. I met a cart driver on the way back and asked him what he knew about mounds? The man reckoned that they would be at least pre-world wars and that there would be treasure hidden in their foundations. Tam-tam! Who knows? He also said that there are other gurus in the area, taller than the ones from Sona, but nobody knows about them, only the locals. Some would be in the village where the cart road apparently led to, the village of Halmeag. The quite detailed terrain map I'm documenting doesn't show there some "peaks" as it looks at Sona in the mounds visited.
Another hypothesis is that there would be some tumuli, which hide the tombs of Scythian or Celtic chieftains, from the time when these peoples crossed these places. Archaeologists have found in the open site around the tombs ceramic fragments from the Late Bronze Age and the Hallstatt period.
A legend, which I believe has a grain of truth, says that these mounds come from from Dacian times. They would hide treasure. That's why no one but treasure hunters have haunted here. On the side, the gills of a mound, you can see scavengers' marks covered in vegetation. For the triangles, there's also the theory that these mounds are part of Dacian magic triangles, including the Dacian capital Sarmizegetusa Regia, the Dacian fortress Piatra Rosie, the sanctuary of Racos, the temple of Sinca Veche and the summit of Omu in Bucegi.
Other legends talk about the yellow earth in the body of the mounds, others that they were built by giants and hide their graves.