Eberras Karrnath

the severing of Karrnath from the main body of Khorvaire was probably the best thing that could happen for the human nations that remained intact after the core-shattering cataclysm 4000 years ago. 
100+miles of open air puts a real stop to warfare.  Once Spelljammer ships developed to cross The Mourn, cautious alliances could be forged while the navies slowly accumulated on all sides. 
Karrnath, moreso than any other area around the shattered Khorvaire, experience Spell Storms rolling up the southern ledge to spill across the landscape. 
This has given rise to unusual locations like the Lightning Forest-- the magic-infused thunderstorm would create jagged lines of stone whenever lighting struck the ground.  Long, jagged spikes of granite became sculptures of the storm's passage.

The northwest edge of Karrnath has become the location of halflings from Athas during the gating of the world into Eberron. Halflings keep to themselves and spend more time exploring the depths of the Karrnath continental walls sinking into the Mourn than harrassing their new human neighbors.