"Stone ships were a burial form used in the bronze- and –iron ages and during the Viking period. They were shaped like acute oval stone circles, and might frame a grave established within the sides of the ship, but they could also function as memorials for the deceased. It is not really known why rich Vikings were buried in this way, but it is believed that the stone ship symbolizes a boat which was to carry the deceased to the kingdom of the dead." Source: Fortidens Jelling.
"Such a stone circle has existed in Jelling [Denmark], a gigantic stone ship 354 metres long. The stone ship is the oldest of the memorials in Jelling from the Viking Age."