Jason V.
Yelp
One of the better preserved castles I toured during my time in Wales, Chepstow Castle looms imposingly over the muddy, plodding, slithering River Wye that coils at its base. Continuing with the serpentine metaphors, Chepstow's outer rampart continues to snake up the hill behind the main fortification for several hundred feet, offering a spectacular view of the countryside (the Wye itself is a muddy brown, and not particularly exciting). There are several chambers and cellars still mostly intact, some of which (along the riverside) egress to narrow walkways along the cliff face.
Unlike some manor houses and estates that identify as "castles" (instead of the glorified stone mansions that they are), Chepstow is the real deal - the vastness of its expanse and volume, the thickness of its walls, and its position atop a cliff, would have made it a bitch to siege.