Oh my gawd. That is so beautiful. Makes me want to be a bird and live in it (clutter-free, minimalist - of course!).
Think before you buy. Cement is both unrelentingly hot and painfully cold, depending on the season. It may be pretty, but could kill it's inhabitants. It's certainly no place to shelter from a snow storm, if you're in a climate that has them.
People aren't happy living in cement block houses, my guess is that birds aren't likely to be either.
Birds normally don't hatch their eggs in the wintertime...
The wooden front continues in the inside of the Rohbau Birdhouse and becomes a parquet as you can ascertain here:
http://tinyurl.com/ygw32nn