From Shaiya Wiki
Above is an image of the 20-30 PvP map. At the time the image was taken, the altar was under the control of Union of Fury. The altar has a hill between the two roads leadng to it, a strategic location if used wisely.
Both sides have a dungeon, which provides quick leveling with the right party, and a "safe" way to acquire lapis without going to the merchant towns Iris (Union of Fury) or Apulune (Alliance of Light) and paying other players in-game gold.
This map is particular challenging in that a single party of 7 with a good strategy can overcome several parties of 7 each.