TREASURE LEVEL 1 - MUSICAL MANIAThe entrance to this level is the same as the 1st Story Level: the back door of the building at the bottom of the airfield. You'll need Indy and someone with explosives either the Russian Officer or Russian Grenadier in order to complete it.
TREASURE LEVEL 2 - TOMB TIMEThe Tomb Doom Story Level entrance in the cemetery also leads to this Treasure Level. In order to beat it, you'll need Oxley and either the Russian Officer or Russian Grenadier.
TREASURE LEVEL 3 - MIRROR MAYHEMOnce you've unlocked either the Russian Officer or Russian Grenadier, have him team up with Oxley to tackle this level. The entrance to this Treasure Level is in the same place as its Story Level counterpart: the tent with the white awning in Spalko's campsite.
TREASURE LEVEL 4 - FOREST FORAGEThis is a vehicle level so it doesn't matter which two characters you use. The entrance is roughly the same as the Rainforest Rumble Story Level. Follow the road below the campsite as it curves around to the right. Just before the Super Bonus Level entrance and the Army Jeep, there's an archway made of branches. Enter there.
TREASURE LEVEL 5 - JUNGLE JUMPOnce again, you'll need a character with explosives, so either the Russian Officer or Russian Grenadier, plus Oxley and his Crystal Skull. The entrance is in the same place as the Dovchenko Duel Story Level: Follow the road leading out the bottom of the campsite, turn left and go past the ant swarm, then continue forward through the archway made of branches.
I do not own, or pretend to own any information above, any information posted above by me is to be used only to help this community and for no other purpose. The original information can be found here: http://brickraiders.net/LegoIndy2/CS2/CS2-treasure.html Any questions please feel free to send me a pm, I am glad to help in any way that I can.