This fictional location was the estate of Colonel Fitzwilliam Darcy. Austen records the picturesque landscape of the estate located in Lyme Park in her description in Pride & Prejudice: 

"They gradually ascended for half a mile, and then found themselves at the top of a considerable eminence, where the wood ceased, and the eye was instantly caught by Pemberley House, situated on the opposite side of a valley, into which the road with some abruptness wound. It was a large, handsome, stone building, standing well on rising ground, and backed by a ridge of high woody hills;—and in front, a stream of some natural importance was swelled into greater, but without any artificial appearance. Its banks were neither formal, nor falsely adorned. Elizabeth was delighted. She had never seen a place where nature had done more, or where natural beauty had been so little counteracted by an awkward taste. They were all of them warm in her admiration; and at that moment she felt that to be mistress of Pemberley might be something!" (259)

Austen, Jane. Sense and Sensibility, edited by Kathleen James-Cavan, 2nd ed., Broadview Press, 2020.