Alnwick Castle in Winter&#x27;s snow. Alnwick Castle is a castle and stately home in Alnwick in the English county of Northumberland. It is the seat of the Duke of Northumberland, built following the Norman conquest.   For those who love &quot;Harry Potter&quot;: -- The castle served as the backdrop for Hogwarts&#x27; broomstick flying lessons scenes.  For those who love &quot;Downton Abbey&quot;: --- The castle served as an impressive backdrop in the show&#x27;s 2014 and 2015 Christmas specials.