I'm stuck at the beginning of level 6. I've got the key to the second gate, but I keep ending up in what I think is the wrong room across the lava canyon. There's no way to cross the lava and there seems to be no other cave to swim to. I've got this walkthrough and it tells me that there should be ladders, but there are none, only a slope that makes me crash into the lava.

I really hope that one of you can help me. Thanks in advance!