Hadrian’s Wall 
It has survived for 2000 years and is a lasting monument to the builders and engineers of the Roman army. The Emperor Hadrian visited Britain in 122AD and due to his policies to maintain the provinces of the Empire, rather than extend them, the wall was built. The south of England had been conquered by the Romans but the North was inhabited by a difficult tribe called the Picts. At this time Hadrian introduced a strategy of consolidation - his objective was to restore order in problematic regions of the Empire. The days of expansion, instigating and financing invasions of new territories in the Roman Empire were past.
What was the purpose of Hadrian’s Wall?
The purpose of the wall was to 'separate Romans from Barbarians'. Hadrian's Wall was a Roman frontier built not just to prevent movement but also to control movement - especially the movement of the Picts. 
Where was Hadrian’s Wall located?
Hadrian’s Wall was built across one of the narrowest parts of England, linking two rivers. Hadrian’s Wall stretched from the East coast near Newcastle to the West coast: a physical border separating  Scotland  from the rest of the island,  not far from the present border between England and Scoltland.
What was the size of Hadrians Wall?
Hadrian’s Wall was a boundary  117 km long (equivalent to 80 Roman miles).  The Eastern section was the first to be built using stone. The Western section was initially built using turf - to hasten the completion of the barrier. At the highest point it was 3.6 metres high and 2.4 metres wide.
The Roman Mile
The Roman mile was 5000 feet (1524 meters). The Roman mile originates from the Latin word 'Mille' meaning a thousand. A Roman mile was the distance a Roman legion could march in 1000 paces.
The Building of Hadrian’s Wall
Who built Hadrian’s Wall? How long did the wall take to build? Hadrian’s Wall was built by Roman legionaries. The men of the Roman Legions were skilled in building roads, buildings and roads. Engineers, stonemasons and blacksmiths played a vital role in the legions. It took about 6 years to complete.
Facts about Hadrian’s Wall
Hadrian’s Wall was a remarkable example of Roman building and architecture, the following interesting facts describe the enormity of the project:
Fact 1: It stretched for 117 Km, was about 2,5 m wide and about 3,5 m high
Fact 2: 80 Milecastles were built along the wall , one every  Roman mile. A milecastle was a huge fortified gateway which Roman soldiers used to go on patrol to the north of Hadrian’s Wall. 

Milecastles were also used to control people who passed through the Wall. The Milecastles housed garrisons of up to 60 troops
garrison=  group of soldier

Fact 3: Turrets (watchtowers)- At regular intervals between the milecastles, turrets were built. Turrets were small towers extending above the Wall. From the numerous turrets the Roman soldiers could keep watch over the surrounding countryside. The Turrets housed garrisons of up to 4 troops .

Fact 5: The Forts, Milecastles and Turrets enabled Roman soldiers to watch what was happening along the whole length of the border
Fact 6: Ditches - On the north side a deep defensive ditch was dug - ensuring that it could only be crossed through the Roman controlled Milecastles or Forts
Fact 7: Settlements grew up around the forts and trading centres were created.

Guarding Hadrian’s Wall
Hadrian’s wall was manned initially by troops from the 2nd, 6th and 20th legions who incorporated men from every corner of the Roman Empire. As time passed the job of guarding the surrounding countryside gradually fell to men who were recruited from the local population. Manning Hadrian’s Wall was eventually viewed as a good job by the local population and the job of manning it was passed from father to son, much as with any other occupations of the era. Hadrian’s Wall fell into disrepair following the decline of the Roman Empire when the Romans left Britain in 410 AD. Stones taken from the ruins of the Wall were used to build local buildings and for the construction of great monasteries such as those built at Lindisfarne. VIDEO: http://www.youtube.com/watch?v=LeosZImCrMY