For example, the logicboard is very small, about the size of the one in the MacBook Air. To the left and right of it, there are two fans and a couple of speakers, and that’s basically it.
The rest of the case is taken up by flat metal enclosures – the resonating chambers for the speakers, presumably. Also interesting: the whole front, including the colored strip under the display, is one piece and can be removed after loosening the connecting adhesive.
Interestingly, the iMac now comes with two small button cells to store the time, for example. Ifixit will reveal why there are now two in a later article.