Knighton is a pretty border town, popular with walkers for its proximity to Offa's Dyke. It's Welsh name, Tref-y-clawdd even means "Town on the Dyke".
In fact Knighton is one of the rare instances where the old English-Welsh border set by King Offa in the 8th century and the modern border actually coincide.
There aren't many attractions as such, but the town is pleasant and is probably one of the best spots to base yourself if you want to walk some of Offa's Dyke footpath.