If I were to run an Iron Heroes game for my next campaign, it would be set in Utolso Varos, the Last City. This, as the name suggests, is the last city on earth, and mankind has retreated to it as the world grows old and fades, and life for human beings becomes hostile.
Like Nessus or Viriconium, Utolso Varos is almost collapsing under the weight of its own history. It is many thousands of years old, and feels it - it is decadent, listless, and resigned, although it still possesses a faded and elegant sort of beauty. It is situated on an island in the middle of a great inland sea, and beyond that sea is the wild, dying earth, peopled by beings wondrous and alien, and scattered with the ruins and remnants of the civilizations of aeons past.
The earth has become so old that its very existence has become tattered and frayed. Time passes slowly, and the light of the sun has become flat and dull. Alien spirits and demonic things from other realities slip through the decaying fragmentary boundaries between their worlds and ours. Those who can practice magic hoard it, as if it might protect them from the inevitable end of all things. Gradually the human race dwindles, and history turns its face away.
And in this world we find the PCs: a bunch of guys with big swords raging against the dying of the light by killing things and taking their stuff.