It is an archaeological conundrum that has baffled generations of experts.
Just how did prehistoric Britons manage to transport the huge bluestones of Stonehenge some 140 miles from the Presili Mountains in Wales to their final home on Salisbury Plain, Wiltshire.
The answer is surprisingly simple. The feat really isn't as hard as everyone imagined.
An experiment by University College London found that mounting huge stones on a sycamore sleigh and dragging it along timbers required far less effort than was expected.
In fact the one tonne (1,000kg) stone whizzed along the make-shift silver birch track when pulled by just 10 people, moving at around 10 feet (3.048 metres) every five seconds - which works out faster than one mile per hour if pulled continually, rather than in the short bursts of the experiment.
The Presili stones from Stonehenge are approximately double the weight as the experimental block, but it is possible that one huge stone could have been brought by a group of just 20 people. The community living in the area during the Neolithic would have numbered several thousand so the absence of just a few dozen people was unlikely to cause any hardship.
Doctoral student Barney Harris, who conducted the trial in Gordon Square, London, a stone's throw from UCL's Institute of Archaeology, said he was surprised that so few people had been required to move the block.
"We were expecting to need at least 15 people to move the stone so to find we could do it with 10 was quite interesting," said Mr Harris.
"It's true that we did the experiment on flat ground, and there would have been steep slopes to navigate when going through the Presili Mountains, but actually this kind of system works well on rough terrain.
"We know that pre-industrialised societies like the Maram Naga in India still use this kind of sledge to construct huge stone monuments. And similar y-shaped sleighs have been found dating back to 2000BC in Japan which we know were used to move megaliths.
"The Chinese also used sleighs to build the Forbidden City and some of those blocks are 123 tonnes (123,000kgs). So in comparison, these are blocks are quite small.
"Some people think they may have been pulled by oxen, but actually oxen are quite belligerent and difficult to control. This experiment shows that humans could have carried out the task fairly easily.
"We now want to go back and crunch the numbers and hopefully from the data we can work out how long it might have taken to bring the stones here."
Stonehenge was built during the Neolithic period, between 4,000 and 5,000 years ago.
The very large standing stones at the megalithic monument, which weigh between 30 and 40 tonnes are of 'sarsen' a local sandstone, but it is the smaller bluestones which have intrigued experts as they can only be found in Wales.
Archaeologists at UCL and the University of Leicester recently found the actual quarries that produced the stones. The spotted dolerite bluestones came from the outcrop of Carb Goedog while Craig Rhos-y-felin, produced the rhyolite bluestones.
The special formation of the rock, which forms natural pillars, allowed the prehistoric quarry workers to detach each stone with minimum effort. They only had to insert wooden wedges into a crack and let the Welsh rain swell the wood and crack the stone, to allow each pillar to be eased away from the rock face.
Stonehenge expert Professor Mike Parker-Pearson of UCL believes the Stonehenge stones were part of a monument that once stood in Wales which was dismantled and moved to Wiltshire. But even Prof Parker-Pearson was amazed at how quickly the stones could be dragged.
"It was a bit of a shock to see how easy it was to pull the stone," he said
The experiment was carried out as part of UCL's Festival of Culture which runs until Friday.