The original Scotland Yard was an area near Westminster Palace occupied by the Scottish Ambassador to the English court. Later an office block was built on the same spot and took the name Scotland Yard.

When it was demolished and a new office block was erected on the same spot it was called New Scotland Yard.

So the old Scotland Yard is beneath the foundations of New Scotland Yard!

Not sure what you mean. Scotland Yard is the name of a street in London. The Headquarters of the Metropolitan Police are known as New Scotland Yard (although they're not located there) but the majority of people just call it Scotland Yard.

Scotland Yard (actually, New Scotland Yard) is the headquarters of the London Metropolitan Police Service. Their mailing address is:

Metropolitan Police Service

New Scotland Yard

Broadway

London, United Kingdom

SW1H 0BG

"New Scotland Yard" is the headquarters of the Metropolitan Police - the police service for Greater London, England. The current "New Scotland Yard" is actually the second building with this name; the first was converted into offices for the UK Parliament. The name "Scotland Yard" comes from a small street off Whitehall in London, where the Scottish Embassy was based prior to the political union of Scotland and England in 1707. The Metropolitan Police later had its headquarters in this street (until the 1880s, when the first New Scotland Yard was built).

Scotland Yard is the name given to the headquarters of the Metropolitan Police in London. The name came from the location of the original offices in Scotland Yard - a street in London which they very quickly outgrew.