Hadrians Wall was the greatest monument left in Roman Britain and the greatest wall ever built in the Empire.
At the time of completion over 24 million tons of stones were used in its construction.
More than all the stones in all the Pyramids in Egypt.
It was the singularly most expensive and costly wall the Romans ever built.
However much of it was used or removed years ago to build roads within the local area.
Now it is a protected National Site. The size, structure and depth of the Wall can be seen from the picture above.
In particular its worth visiting Wallsend to see this rebuilt section.
http://ancienthistory.about.com/od/architecture/ss/042209HadriansWall_2.htm
The Romans assaulted Scotland with more soldiers than was used to hold the whole of England and Wales:
See the link of evidence below: