The North Pole is at the Head of the lake in Winter Holiday. The North Polar Expedition plans to travel to the North Pole. Nancy says .... nothing ever happens in the winter time ... so we started a Polar expedition. Peggy adds as soon as we could we'd go to the North Pole over the ice .... . Only Nancy and Peggy had been to the North Pole, but a long time ago (WH23).
Peggy tells them that It's right at the head of the lake. The extreme north of the Arctic, and only a few yards off the ice. You can’t mistake it (WH23). The North Pole building is an old summerhouse known as the old view-house where the old man who built it just over a hundred years ago watched the Lake out of a big bow window .... in all weathers and all seasons .... behind windows that could be thrown open in summer , and with a fireplace so that he need fear no cold in winter. It is one story high with a little chimney at the back, and a tall flagpole on which Dick puts the tiny yellow quarantine flag (WH26).
Nancy sees a light lower down than the lights of the village where there is nothing except .... and then sees the Ds long and short Morse flashes reading "N.P." (WH25). The D's sledge has a smashed mast but the main thing was that they had found shelter and the Pole. Nothing else mattered (WH26). But later in a "native moment" Dot says We've got to go home (unrealistically; to leave shelter for a night return in a blizzard!) though Dick reminds her that they have signalled and they might miss the others in the dark (WH28).
Captain Flint told them earlier I've got to make sure that those particular (polar) bears will let us have the key. Dick asks Key .. to the North Pole? (WH23). He has stocked it with sacks of coal (WH23) and a packing-case marked "N.P.E.'" of food enough to last a dozen people for a whole day: two cold chickens and a Christmas pudding and what not, with plates knives, forks, spoons and mugs .... nine of everything (i.e. a set each; including Captain Flint and Nancy) (WH28). Before Captain Flint returned, Nancy when talking to the doctor decided that now was not the moment to talk to him about the transport of hampers and coal-sacks and getting the people who owned the North Pole about the expedition having the use of it(WH20).
On their maiden voyage in Scarab to the head of the Lake, Dot points to the little summerhouse with its flag staff. (PM26)