At the Venice screen type in the cheat codes below; you will hear a beep and see a message if done properly.

HDIVIEW - Reveal Map
HDIKASH - 50,000 Florins
HDISPY - See Actions of Opponents
HDIKARNAGE - Activate Inactive Mercenary Groups

SOURCE: http://www.actiontrip.com/cheats/machiavellitheprince.phtml