Old Rachival, the original home of the gnomes, is filled with undead and rogue automatons that don't take kindly to visitors. New Rachival, which is where portals lead, is filled with the normal type of gnome, though not necessarily less dangerous, depending on if you walk in on a gnome in the middle of an experiment. :P
All the cities available from the portal listings are safe, and you are free to explore them. The only other cities I can think of that aren't an "original" home to the race that now lives there are Mahagra, Sslanis, and, I guess, Dalimond.
Half-giants originally hail from Trandalar, but they left a long time ago, and I haven't ever really found any traces of an original city there, if there was one. Trandalar is a T3 area. It does have a deadland, but the majority of it is either safe or populated by more normal creatures.
Sslik were originally a nomadic race; Sslanis is the first permanent place they have called home. I've found at least one ruined sslik building in the world, in the Spiritous Swamp, I believe, but that's a very dangerous place to go.
Dalimond is not really a city established because of the loss of a previous one, but it's not the "original" city of the humans. As far as I can tell, humans have always been clustered in the Dalimond Peninsula, though there were some truly ancient civilizations of them in the Tazoon desert, of which ruins can be found.
The satyr and the dryad do not have their own capitol cities in the game-world. The satyrs' capitol, Bachan, lies beyond the Eastern Deadlands and firmly in the grasp of the Withered Aegis just like the rest of Eastern Aradoth. I believe that there is a small refugee camp of satyr in Feladan though. The dryad city of Palmyra was, if I remember correctly, removed from this plane of existence entirely by the dryads themselves, in order to avoid the Withered Aegis.