This is the 8749th most frequent Swedish word.
byggda
"Byggda" means "built" or "constructed."
Here, 'byggda' is used as an adjective describing the construction type, though the phrasing may seem grammatically unexpected due to agreement in gender and number.
Staden är byggda nästan uteslutande av trä.
The town is built almost entirely of wood.
In this sentence, 'byggda' describes 'broarna' (the bridges) and specifies that they are ones that have been constructed.
De byggda broarna har stått i hundratals år.
The built bridges have stood for hundreds of years.
In this case, 'byggda' serves as an attribute for 'stenhus' (stone houses), emphasizing their built nature.