The Blue Mosque is one of Istanbul’s two great historic religious buildings, Hagia Sofia (almost next door to it) being the other. The mosque is a fully-functioning place of worship and tourists are admitted only between services.
It is very beautiful, both inside and out, and has a grace and lightness belying its size. The interior is spacious but welcoming (not inhuman and alienating like, for instance, similarly large open spaces in airport terminals!) and serene in spite of the crowds and cameras; I could happily have sat there quietly for an hour. The other thing I wanted to do – and did – is point my camera upwards to the gorgeously decorated pillars and domes.