Humans have spent centuries studying Stonehenge, yet it still has a few tricks up its sleeve. Research reveals that the size of the world’s most mysterious megalithic monument is much larger than previously assumed, giving enthusiasts a whole new set of questions to ponder.

While many secrets of the sacred site will remain hidden, here are some impressive stats about Stonehenge that have come to light.

1. It has long been thought that Stonehenge stood in isolation, but new research — described in the BBC Two documentary "Operation Stonehenge: What Lies Beneath" — employed techniques to scan the earth below the surface and has uncovered something different. Underground maps show 17 previously unknown shrines and hundreds of other archeological features around the site, including types of monuments never seen before.

2. Stonehenge dates back to around 5,000 years ago. It began as an earthwork — a bank and ditch called a henge. Archeologists think that the ditch was dug from tools made of red deer antlers; the chalk underneath was likely removed with shovels made of cattle shoulder blades.

3. Merlin the magician, the Romans and the Druids have all been given credit throughout the centuries for building Stonehenge, but now archaeologists think that the first stones were raised around 2500 B.C. by the native inhabitants of late Neolithic Britain, according to English Heritage, the government body that looks over England’s historic sites. Researchers generally believe it was built to track the sun’s movements, in particular the summer solstice.

Stonehenge circles The stones of the inner and outer circles. (Photo: Danny Sullivan/Flickr)

4. The first section, the inner circle, is comprised of about 80 bluestones that weigh a whopping 4 tons each. The stones were quarried in the Prescelly Mountains at a site known as Carn Menyn. Remarkably, the quarry is located more than 150 miles from the site. Modern theories suggest that the stones made the trip courtesy of rollers, sledges, rafts and barges.

5. Why they would select stone from so far away remains without a definitive answer. One theory claims that the builders believed that the rocks of Carn Menyn were endowed with mystical properties for recuperation, and since visiting the mountains was difficult, bringing the stones to Stonehenge was a way to create a more-accessible shrine for healing.

6. The giant stones that form the famous outer circle are made of sarsen, a type of sandstone. Most experts believe that these stones, weighing an average of 25 tons, were transported about 20 miles from the Marlborough Downs. The largest stone, the Heel Stone, weighs about 30 tons. While much of the route was (relatively) easy, modern work studies estimate that no fewer than 600 men would have been required to get each stone past Redhorn Hill, the steepest part of the journey.

7. To raise the stones, a large hole was dug, with half of the hole lined with wooden stakes. The stone would be moved into position and forced upright using ropes and possibly a wooden structure; the hole was then packed tightly with rubble.

8. To secure the upright stones with the horizontal lintels, Stonehenge’s builders made mortise holes and protruding tenons to ensure stability. The lintels were then fit together using tongue and groove joints.

summer solstice at Stonehenge Thousands gathered at Stonehenge in 2014 to witness the sun rising on the summer solstice, the longest day of the year. (Photo: Paul Townsend/Flickr)

9. While those who have never visited Stonehenge may imagine it as a sacred site secluded in idyllic natural surroundings, in fact, there is a major highway less than 100 yards from the stones; in addition, the site is surrounded by what calls “a commercial circus,” complete with parking lots, gift shops and cafe.

10. Stonehenge has become such a recognizable symbol that it has made cameo appearances in no shortage of cultural features. It was in the Beatles film “Help!,” Roman Polanski's "Tess" and the classic mockumentary “This is Spinal Tap.” It has shown up in books, computer games and television shows. And let's not forget "National Lampoon's European Vacation," in which Clark Griswold bumps into one of the stones in and knocks them down, one by one, like a giant stack of dominoes. The Neolithic builders would not be pleased.

10 curious truths about Stonehenge
The world's most famous ring of standing stones has been studied for centuries, yet we learn something new about it all the time.