I am sometimes asked what my favorite work of architecture is. Rather than name a historic or popular icon, I usually respond by saying that I like buildings that help build neighborhoods and communities. But if pressed to name one, I can only narrow the list down to two: the Pantheon in Rome and the Hagia Sophia in Istanbul. Both are ideal in conception and outlook but also enduringly attractive in the way they have aged and adapted to different uses over the centuries. It is only over time that any design can be truly evaluated for its worthiness.