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It took a whole night to climb Mount Fuji.
Literal
Fuji-mountain [to-に] climbing [for-のに] whole-one-night took.
丸一晩 ('a full one night') uses 丸 as the prefix meaning 'whole, entire.' ~のに ('for the purpose of') marks the action that required the time. かかった is the past of かかる ('to take time/cost'). A simple but vivid sentence about Japan's most iconic mountain.