Why so intriguing?

These, and more, are the reasons why they are so intriguing:

They are called “Pictish” but who erected them?

Why is there a gap between the naming of the “Picts” by the Roman invaders around the late 3rd Century CE and the generally suggested dates for the erection of the Stones? Or are previous estimates incorrect?

Did the existing population erect the Stones – or was it by incomers?

Who had the skills to carve the Stones; and why onto a material that has endured so long? Was this choice of material deliberate?

What do the symbols mean – assuming they do have a specific purpose and give a particular message?  Were they for worship, boundary markers, burial indicators, commemorative of specific events, used to educate – or maybe just decorative?

Are the Stones located in significant locations?

Why did the symbols on the seemingly older Stones carry forward to the newer ones with Christian crosses?