The pride of Lord Splyncrith's empire was the city of Splynn on the continent of Atlantis.  However, Lord Splyncrith lost his life in an epic battle that happened right out in front of his massive pyramid. (See page 36 in Atlantis for a picture of the exact battle area where the deed happened).
This area, including the 4000 foot high massive pryamid, rests on one of the the planets most powerful leyline nexuses.  This is the reason Splynn was built here.
It is rumored an odd being with strange powers named Jack thrust a greatest rune sword into the Lord of Atlantis while casting a spell of legend on the nexus during a time of supreme power.  The result was a permanent Sanctuary spell covering a 5 mile radius right in the heart of Splynn.  The area the spell affects include the Pryamid, The Arena of champions, The royal Bio-genetics medical center, the Splynn zoo, several royal buildings and part of a forest preserve.
The group that dared to create this magic quickly departed Splynn.  GlenKryth, SusanCryth, and the rest of their royal godlike court quickly regained control of the city.  However, they were and still are unable to remove the sanctuary spell and thus have no way of using force in the area.
Two years later Jack returned to claim his new kingdom with the help of some powerful friends.  Jack is able to cast spells and do harm inside the sanctuary.  He also has complete control of the pyramids mystical properties and forcefully removed all Splugorth followers and other creatures and beings he declares obnoxious.  He has proclaimed his new kingdom Jacktown.  Escaped slaves from the continent have flocked to the little area and it is a bustling little town. It is haven for fairys in particular and 40% (sometines more) of its population are accounted for among the fairy folk.
Some highlights of Jacktown
The Pyramid of Jack- Formerly the focal point of the Splugorths power in the city, Jack takes residents here and has opened up the massive structure to anyone that cares to explore it, sleep in it, etc.  The wonders of Splyncryth's empire lay hidden inside for anyone to see.  It is a massive 4000 ft high with a massive girth.  Bars, curiosity traders, brothels, etc, have begun to pop up in its interior as well as residencies.  Splyncryths massive personal living space is now shared by Jack and includes Lord Spylncryths personal collection of art, books, magic, weapons, etc.
2.  The Arena of Champions (see atlantis bk 3).  No real contests here now but it is still crowded usually with concerts, traveling shows, circus, etc.  Jack pays premium for entertainment and provided transportation to and from the area.  An Adirok Flying mountain sometimes sleeps there as well.
3.  The royal zoo's former captives have mostly been liberated and replaced with demons, deevils, undead, and Splugorth highlords.

The town is mighty chaotic w/o any real laws.  Splynn has been relocated and is close to its former glory.  The area outside the sanctuary spell is crawling with splugorth and it can be perilous still reaching Jacktown.

Rough Pop breakdown
Thousands of fairy folk (including the scary ones).
4 dragons stay there (2 chaing-ku, thunder lizard, and an ice dragon) but others are transient.
about 3000 escaped slaves (varying races from the Atlantis books).
Also transient beings, merchants, wizards, etc that come and go.  The nexus is a place of power and any who come are welcome to tap into it.  Also, fairy weapons are paid for in premium and one can always sell them at least 50% above the highest known market value.  No questions asked and no real haggling.  The fairys are then set free to do whatever the hell they want.