Many secrets remain surrounding the creation of Stonehenge. Archaeologists try to unravel the mystery.

Salisbury Plain in southern England. 2500 BC, the same time as the pyramids in Egypt are under construction, workers here complete the outer circle of Stonehenge. They haul huge rocks, some weighing up to 45 tons across rough terrain. They work each granite-like stone into shape, then pull them upright to form the great stone circle. Thousands of people work on this massive project.

When they complete this phase, an inner horse-shoe of five great arches will be enclosed by a ring of 30 stones upright and topped by a circle of perfectly horizontal stones called lintels. But while we know this was an incredible feat of engineering, who this people were and why they built Stonehenge has remained one of the great unsolved mysteries of the ancient world.

SALISBURY PLAIN= Salisbury is an important old city in the South of England and PLAIN is a flat area of landscape.

2500= Years are read in two groups (25-00), so the first group here is "twenty five" and the second group "hundred".

BC= Before Christ.

OUTER= External, located in the outside.

CIRCLE= /sɜ:kəl/

HAUL= To pull or drag, especially with effort.

HUGE= Immense, very big.

WEIGHING= from the verb to weigh. If you weigh 70 kgs, that is how heavy you are.

TONS= /tʌnz/ A ton is 1000 kgs

ROUGH= /rʌf/ the opposite of smooth and flat.

TERRAIN= An area of ground.

GRANITELIKE= As hard as granite stone (see picture of granite)

INTO SHAPE= If you work something into shape, you manipulate it to give it a specific form.

UPRIGHT= In a vertical position.

MASSIVE= Immense, huge.

INNER= Internal (the opposite of outer)

HORSESHOE= The curved piece of iron you put on a horse hoof (its feet) to make them more resistant. Here, it is used as an adjective to show the shape of the row of stones.

ENCLOSED= Surrounded.

TOPPED BY X= With X on top of it.

LINTELS= The horizontal stone, piece of wood, etc. placed on top of a door, window, etc. to support the wall above it. But in Stonehenge lintels don't support anything (as far as we know).

FEAT= A very impressive action.

UNSOLVED= Not solved, still unknown.

ANCIENT= Very, very old.