The Pre-Cave is the room right before we get to the Molecular-Fusion-Generator, the power supply for the Time Riders.

While we are in the Pre-Cave we get seperated by the Tour Guide in (up to 8) groups of 20 persons. This seperation also sets the time rider you will travel in. 

The seperation is done from left to right, so that the very left lane will be Time Riders 1 and the very right Time Riders 8.

Now we have to wait until the doors in front of us will open to proceed to the Molecular-Fusion-Generator.