Sessrumnir

Sessrumnir, or the Hall of Many Seats, is Freya’s mansion in Folkvanger. It is also intended to be a ship for the residents of Folkvanger to use during Ragnarok.

The Sword of Summer
Sumarbrander drags Magnus Chase and Blitzen to Folkvanger while they are trying to go to Nidavellir. They go to meet Freya in her mansion, Sessrumnir.

Magnus later realizes that it is an inverted longship that can house tens of thousands of passengers. Freya mentions that she and her subjects shall use this ship to travel to Virgidr, the final battlefield, during Ragnarok.