Nests would be a nice decor element!
You can make the big blocky structures look good with some architectural flourishes added to the exterior and roof treatments, but it still winds up being massive. I got some great ideas from Share my house West Fan Village, and added some of that to my Colosseum to make it look a lot fancier. 
Been running some arithmetic and also found that you could house a map room inside a giant pyramid as well.