Pass the putrid tunnel.

Complete the TAIGA level.

Stand your ground against the Bear at first encounter.

Complete the CASPIAN level.

Find the maps in the Labaratory.

Kill 90 cannibals.

Find a tune on the radio.

Duke survives.

Find the passenger train car.

Kill the Catfish.

Kill 3 enemies using sniper scope while wearing the Gas mask and using the Night Vision goggles all at the same time.

Get into a boat.