 At the very core, the mosque is the sacred place of Islam. It is where men and women and children go to pray. And so almost any place can be a mosque. Every mosque attempts to be facing the cardinal direction of Mecca, which is considered the sacred spot on earth. It's a concavity that marks a small absence space where Muhammad used to stand and lead prayer. I've been studying mosques and Islamic architecture now for over 20 years, but then I started to look up to the sky a little more carefully in more recent years, and I was realizing that a number of mosques that were constructed in Istanbul and other areas of what used to be Ottoman lands include birdhouses on their walls. And these birdhouses can be simply little holes that are purposefully there, or they can be small perches, or even more elaboratively, they can be what is known as bird palaces. But architects, especially from the 16th and 18th century, were obviously thinking about the mosque also not just as a place where men pray, but a place where birds and live and sing.