From George R.R. Martin:

This Iron Throne is massive. Ugly. Assymetric. It’s a throne made by blacksmiths hammering together half-melted, broken, twisted swords, wrenched from the hands of dead men or yielded up by defeated foes… a symbol of conquest… it has the steps I describe, and the height. From on top, the king dominates the throne room. And there are thousands of swords in it, not just a few. This Iron Throne is scary. And not at all a comfortable seat, just as Aegon intended.

[Source: George R.R. Martin | Via Buzzfeed | Painting by artist Marc Simonetti]