Caernarfon Castle.

Legend has it that
the Welsh petitioned
Edward I to appoint someone
as the Prince of Wales
who: spoke no English,
had never told a lie,
and was born in Wales.
To their surprise, the king
agreed. He then gave the title
to his infant son,
Edward II, born just days earlier
in Caernarfon Castle.

The Prince of Wales has
since been invested at
Caernarfon, the most
recent of which was
Prince Charles.