In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.
Q: Article: For centuries Stonehenge has mystified and enraptured archaeologists and visitors. So maybe it is not surprising that another monumental wonder from prehistory has been overlooked for so long - even though it is just a mile away. Experts have discovered an 'extraordinary' line of giant stones that dates back more than 4,500 years. The area around Stonehenge is littered with prehistoric sights but the 90 or more stones, lying 3ft underground, have only just been discovered by sophisticated radar equipment towed by radar equipment. The buried monoliths are each up to 15ft tall. Instead of being arranged in a circle as they are at Stonehenge, it is thought they once formed a long standing line. 'We are looking at one of the largest stone monuments in Europe and it has been under our noses for something like 4,000 years,' said Professor Vince Gaffney, from the University of Bradford, one of the archaeologists leading the research. 'It's truly remarkable. We don't think there's anything quite like this anywhere else in the world. This is completely new and the scale is extraordinary." Prof. Gaffney believes the stones may have been planted by the same people who built Stonehenge, but he doubts whether there is a direct link between the two monuments. These stones were placed along a steep slope, cut into a natural dry valley to form a C-shaped feature. Precisely why the stones were put there remains a mystery. The archaeologists believe that at some stage the stones were pushed over. This was not done to damage the monument but rather to preserve whatever it was about the stones that seemed so important. "There was a transformation in the landscape that we do not understand," Prof. Gaffney said. "The stones had significance. These were special places. Societies were organized, as with the great cathedrals, to create these things."
Answer: It is the largest stone monument all over the world.
A:
What can we know about Stonehenge from the passage?