Built on the site of an earlier castle built by Llewelyn ab Iorweth, in 1277, King Edward I ordered the construction of several formidable castles. They included Flint, Rhuddlan, Builth, and Aberystwyth. All these castles have survived and are accessible to the public. Of these four castles, two led the way into the future of castle construction. Designed as concentric fortresses, Rhuddlan and Aberystwyth Castles were innovative structures composed of rings of defenses, walls-within-walls, which allowed guards to defend their stronghold from several heights without firing upon their own men. Of the two castles, Aberystwyth is the most ruined, but in its heyday, the castle was every bit as intimidating and secure as its cousin in NE Wales.(The above is an extract from the excellent website [www.castleswales.com] and with kind permission of the author of many an historic essay on the various castles in Wales, Mrs Lise Hull.)