1) Landing pads. Paint an ID letter/number on it
2) Stick a few 'crumbly' bits of walls around the edge. You'll have aruin.
3) Paint it up as if it was liquid. Add to the illusion by having something,
(head, arm. tentacle) sticking out of the 'liquid'.
4) Score it heavily almost diagonally. Then snap it. Glue the long sides together
for a fortress ruin.
5) Hit it with a hammer (safety glasses on) & glue the bits together in a different formation.
Cover with a mixture of PVA glue, sand & sawdust. voila, jungle covered ruins.