Age of Discord: The Law Havens · 8:57am
The Havens are areas where some strong emanation of Law weakens the powers of Chaos. This is usually due to the presence of some powerfully-Lawful artifact, such as the Crystal Heart or the Lawstone. Paradise Estate was once such a place, until Discord shattered the Rainbow of Light: now, it's just a ruin, more dangerous than most because Discord sometimes comes here to brood over his lost friendships with the Undying Ponies.
Discord dislikes active Havens because his powers are weakened by them, and close exposure to powerful Artifacts of Law actually pain him. So, he generally avoids them, and his spells usually cannot directly affect them. Even his chaotic creatures are generally weaker in here. If Discord wants to affect events inside a Haven, he must generally do so in an indirect fashion, by attacking unprotected areas on which it is dependent or sending mundane minions in to attack them.
Both because high civilizations often possess artifacts of Law, and because during the Age of Discord possessing such an artifact was an immense advantage which tended to attract scholars, statesponies, traders and other bringers of high civilization, Havens were centers of high civilization in the Age of Discord. A reasonable expectation that one's efforts would not be suddenly negated by Discord's whims or the random depradations of his monsters obviously made it more attractive both to most Ponies and most other sapients.
This does not imply that Havens are entirely safe places.
First, Havens are valuable, something well-known by their current owners. This makes them desirable conquests by forces other than those allied to Discord. Intrigue, violence and outright wars may focus on Havens for precisely this reason. The Crystal Empire has frequently seen coups, riots, rebellions and even civil wars.
Also, Lawful does not necessarily mean Good, so Havens may well wind up ruled by cruel tyrants. The White Queendom of the Heartspire decayed into a depraved dictatorship during the Age of Discord. Even less extremely evil Havens could be dangerous to visit: the customs of the Hegemony of Lith are rigid and its judges harsh and unforgiving even to outsiders who unknowingly violated them.
Thirdly, Discord resents the existence of the Havens, because they limit his power and the scope of his domain. He wants to destroy them, and being superpowerful and superintelligent there is much he can do to harm them and their occupants. Indeed, were not Discord also very lazy, he would doubtless have smashed the Havens long ago.
While Discord cannot easily launch direct attacks on the Havens, there are many ways he can indirectly attack them. Many of his minions can bear the emanations of Law better than can he himself, and some are entirely unaffected by them. Many of the Havens are dependent upon hinterlands which their own Lawful artifacts protect less effectively than their metropolitan cores, and hence are more vulnerable to attack.
Discord can also interfere with Law Havens in subtler ways, and indeed such subtle actions are more characteristic of him than are direct attacks. Discord loves to play, and his favorite form of playing is to manipulate others into creating disharmony. Discord very frequently, whether in his own right form or in shapeshifting disguise, either enthralls or simply tricks victims into serving as his agents inside Law Havens, primed to incite rebellions and civil wars, with the ultimate aim of destroying either the Haven or its protective artifact.
Finally, Discord is not entirely unable to directly attack some Law Havens. If he expends sufficient time and effort, he can unravel certain kinds of Law based defenses; and he can overpower weak Lawful Artifacts. There are also some he cannot overcome, but Discord for obvious reasons does not let others know just to which artifacts he is most vulnerable; nor can his occasional utterances on the matter be necessarily trusted.
With all these caveats, the Law Havens remain centers of what high civilization survives in the Age of Discord -- because Ponykind, and other races, simply have nothing better. And they make the best of what they have, as they have no other choices.