They're models of Swedish houses. You can take them apart and put them back together again, so not only are they pretty but there's a puzzle element to them too (a bit like my wife). I buy one whenever I'm at the airport in Stockholm panicking over not having bought any gifts to bring home.
These houses don't normally live on the office windowsill. Their usual home is on the cabinet we have all our music and DVD hardware in, where we can see them and a few other assorted ornaments I've brought home from trips that my wife feels she ought to display but not in a manner that suggests she wants any more of them. The reason they're on the windowsill is because it took my wife two days to clean the house ready for my daughter's 18th birthday party on Friday, but it's going to take more than two days to restore the place to normality. She may even have forgotten that I have the houses there, so won't find them until next time she comes back with the vacuum cleaner (which, given that it's the dustiest place in the house, either won't be long or will be long, depending on whether she's in "stitch in time" or "nine" mode.
I'm thinking that if I get enough of these houses, I can take them all to bits at once and then build a single, massive, Frankenstein house out of the components.