Large clickable boxes as navigation with CSS and DOM

A client asked for a proof of concept how you could create large clickable boxes as a navigation. They wanted the whole box clickable, and if the link is a section link with child elements they wanted an indicator that there is more. The links without children should simply send the user to the site, the parent links should not follow the main link, but expand the children.

Check out the demo page: large boxes as links and feel free to get inspired. If wanted, I can write a quick explanation on how it is done and you could send sexier styles.