Simplifying would do good. You could have just something like:

VB Code:
  1. Type MySolarSystem

  2.     Name As String

  3.     X1 As Long 'top left corner in the map this solar system starts

  4.     Y1 As Long

  5.     X2 As Long 'top right corner

  6.     Y2 As Long

  7.     X3 As Long 'bottom left

  8.     Y3 As Long

  9.     X4 As Long 'bottom right

  10.     Y4 As Long

  11.     'you can simplify the position by having rectangular areas...

  12. End Type

  13.  
  14. Type MyPlanet

  15.     Name As String

  16.     Info As String

  17.     X As Long 'position in the solar system

  18.     Y As Long 'solar system is determined by the X and Y values

  19.     Inflation As Single 'can hold decimals unlike Long

  20. End Type

  21.  
  22. Type MyCity

  23.     Planet As Integer 'index to Planets array

  24.     Name As String

  25.     Info As String

  26.     Weather As Byte 'you can have 256 different weathers this way

  27.     Inventory(999) As Integer 'you can have 1000 different item types this way

  28. End Type

  29.  
  30. Public Solars() As MySolarSystem, Planets() As MyPlanet, Cities() As MyCity

  31.  
  32. 'just some random example...

  33. Sub Initialize()

  34.     ReDim Solars(9)

  35.     ReDim Planets(49)

  36.     ReDim Cities(499)

  37. End Sub

A lot depends on how big, configurable and random you want your world to be. The bigger the world, the more data it requires. What I've shown here is pretty much as low memory use you can get with your project. Good luck!