This eternal flame represents the jews that in WWII were carried away from this place in the "Hollandsche schouwburg" amsterdam to the concentration camps. The "Hollandse schouwburg" was a theatre that was used by the germans to collect and register the jews that where taken away and is now a national monument. The pebbles around the flame are an old jewish use to show that you have visited the grave. For more information about the monument you can visit this link.
I dedicate this one to taphophile tragics.