I got stuck. I just got those plants from Killer Croc's Lair and i need to return to Batcave to mix something or make some antidote i dont remeber. But I CANT FIND THE ENTRANCE TO BATCAVE!!!!!!!! Please help me, i wana finish this game before i return it tonight

after going to croc's lair there is a secondary entrance from the sewers.  off hand it's something like this.

when leaving crocs lair take a right (over the water)

go through a door and head lefts (south).

at the end of the sewer look up on the right hand side (i missed this enterance the first time too actually).

ohhhhhh, i see... You see, i messed up pretty bad. I got out of the cave and start looking for batcave entrance and running around the iceland like and idiot. So i should get back to the sewer and search for secondary entrance?

yeah, i did the same (mostly becaue i was looking for all the collectibles) and took me a while to get myself back into the right place.  if i'm not mistaken you literally can't access the original enterance at this time so looking for it is a waste.  there is a "cut scence" you'll go through when you go in the back enterance so yeah, go back to the sewer and search from there.  south westerns section of the sewer map is the general location.

how do i go back to the sewer?

Not sure if this helps, but give it a bash.

"Go to the intesive treatment go all the way to the secure transit, jump down the second elevator. by this i mean after you jumped down the broken one, jump down the second one. then you should see a red door somewhere down there go through it you will now be in crocs layer. Countine from what everyone else has told you. Which is go past crocs entrance then zip to the other side and take left once through that door you will beable to get to the bat cave from there."

http://au.gamespot.com/xbox360/action/batmanarkhamasylum/show_msgs.php?topic_id=m-1-51058846&pid=952337

thanks guys i'll try it out