[DGD] Best method to make a wilderness map

["Mario A. Barragán L."]

Hi, i'm trying to make a big grid of rooms, something like 200x200, i'm 
based in a map
i have in ascii, i'm using a system of coordinates, and creating clones 
of the rooms, but the memory is going up very quickly, with about 5000 
rooms loaded, the driver uses 60M aprox of ram, and loading new rooms is 
getting slow, is that normal for that amount of objects loaded??

I've made a room based in the movie "Cube", that simulates an area of 
20x20x20, and you can walk freely and the descriptions are dynamic, etc 
i've thinking in a solution like this, but every time you "change" of 
room, everything you drop, made, etc in the last one disappear, also you 
can't meet any other player.

Does anyone have a vetter solution?? idea??