Standing in considerable decrepitude in the town centre, Hay's battered castle is closed to the public but there are various interesting shops to explore in its grounds, including an honesty book stall (50p per book). This was one of the earliest Norman castles to be built in Wales. A grand manor house was grafted on in the 17th century, but this too is in a precarious state.
Richard Booth became king of this castle, buying the dilapidated remains in 1961. It's now owned by a trust who are intending to restore the complex and convert it into an arts centre.