The town is built around the connection of two rivers: the Ouzel (also known as Lovat) which comes up from Leighton Buzzard and the Ouse which omes up from Buckingham. Once joined the Ouse goes on to Olney and Bedford.
The town was part of Buckinghamshire until 1974 when the government created the new borough of Milton Keynes. Newport Pagnell remains outside Milton Keynes} and cermonially still part of the old county of Buckinghamshire, so it is both within and without Milton keynes depending on exactly what you mean.
As at 2010 there is still some green belt between the town and Milton Keynes but that is shrinking.
Newport Pagnell is probably most famous for:
a) Being the place Aston Martin built their luxury sports cars (there is still a service centre left, although the factory has gone)
b) Tickford Bridge, over the River Ouzel (or Lovat), was built in 1810 and is the only iron bridge in Britain that still carries main road traffic and is the oldest iron bridge in the world that is still in constant use.
c) being the original end point of Britain's first Motorway the M1 where the motorway services still stand.
The Town football team are nicknamed the Swans, after the county symbol for Buckinghamshire.