Buildings are, in themselves an oddity, when you think about it... We sometimes say that humans are the only animals to build complex structures, but this is not true! many animals also build structures, like rabbit holes, or nests.
there are lots of different types of buildings, some are pointless, some are neccesities. there are buildings in which things are manufactured, buildings in which people used to relieve themselves, buildings to wait for a bus in, and Buildings that emulate the outdoors, buildings to film porn in, buildings for chickens to not get wet in... even buildings for buildings!
Some interesting structure types:
Especially odd buildings: