On the way up to the Jungfraujoch, the Jungfrau Railway stops briefly at Eismeer (aka "Sea of Ice"), a viewpoint inside the tunnel at 3,160 meters above sea level.

The train stops for 5 mins so passengers can exit the train and enjoy the glacier view through large windows. The view is spectacular but it's hard to take pics because of the glare. Also, it's often in the clouds, so don't get disappointed if you can't see anything.

Since you don't have a specific reserved seat, you may want to leave a jacket or something on your seat to hold your spot. But bring your valuables with you.

There is a toilet at this stop, but make sure you go quick so you don't miss the train. It won't wait for you.

The train does not stop at Eismeer on the way back down.