I've bought a ton of build-your-own paper buildings from
WorldWorksGames. They also produce some preprinted terrain that you just punch out and assemble. They are, to me, the gold standard for this sort of stuff.
"The Maiden" - their galleon, is one of my most favorite items - I printed and put one together for our Pirates D&D games a few years back and still have it on display in the gameroom (with the party's "Black Hand" pirate flag flying on it).