Before the recent tragic events surrounding the murder of little April Jones by Mark Bridger, Machynlleth was know to most people only for its proximity to the Centre for Alternative Technology and, possibly, for its connections with Owain Glyndwr.
On 16 September 1400, Glyndwr started the Welsh Revolt against the rule of Henry IV of England, but was ultimately defeated by the superior artillery and ships of the English under Prince Hal (the future Henry V) in 1409.
In 1404, he called his first Parliament (or more properly Cynulliad or "gathering") of all Wales at Machynlleth where he was crowned Prince of Wales and announced his national programme.
Tradition has it that this meeting took place in Parliament House in Heol Maengwyn. Unfortunately recent dendrochronological sampling has shown that the roof timbers of this building were felled in 1470, so although very old, it is unlikely to be the actual building.
The building is theoretically open to the public as part of the Owain Glyndwr Centre telling the story of the Welsh uprising. However, at the time of writing (2013), the centre's funding was under threat and, when I was there, it was not open on a day when according to its web site it should have been.