Enter these codes at the 'Password' screen to unlock the corresponding level in the game.

Unlock Amazon River Level:
Enter the code DJNKJGDTMMJR

Unlock Australia Level:
Enter the code LTQRBCTTKSPN

Unlock China Level:
Enter the code LHLKGNPGDBSG

Unlock Greece Level:
Enter the code GLQNBCTTGPLT

Unlock Switzerland Level:
Enter the code JNSMDNHHSCFH

Unlock Tasmania Level:
Enter the code BLJNSJCNMPHS

Unlock Transylvania Level:
Enter the code GNQLBFKQQLBQ

Enter the password JLSNDMHKSFFK to skip to level 5 and have 21 Medallions.