Pemberley, Mr. Darcy's estate, represents Darcy's worth--his literal financial worth, his worth as a person of integrity, and his worth as a partner to Elizabeth. As Elizabeth enters the halls of Pemberley, it is almost as if she is stepping into his life, where she gains new ideas about Darcy's true value.
Chapter 43 goes into great detail about Elizabeth's reaction to the estate. She is taken aback by its beauty and good taste, and marvels at how gigantic and incredible it is. As we all might feel when stepping into a mansion owned by a potential marriage partner, Lizzy feels a twinge of regret at having turned down the owner of this beautiful place: " 'And of this place,' thought she, 'I might have been mistress! With these rooms I might now have been familiarly acquainted!' " She realizes Darcy's financial worth anew, now that she's standing inside its physical manifestation.
Then, when talking with Darcy's longtime servant, she learns that those who worth in his household consider Darcy to be simply the best man on Earth: a gentle, true, and kind master. Mindful of the fact that a household servant could easily complain about his or her master, Elizabeth has a new realization that Darcy's character may indeed be as immaculate as his home, in contrast to her initial assumptions about the kind of man he is. It's as if the beauty of Pemberley is directly reflective of Darcy's personality.
As she ponders these things, and has a courteous, pleasant visit with Darcy himself, Elizabeth fixates on Pemberley as a possible representation of a love between her and Darcy that could still be rescued. Watch what she does as her aunt and uncle try to show her other picturesque scenery after they leave Darcy's estate:
Her thoughts were all fixed on that one spot of Pemberley House, whichever it might be, where Mr. Darcy then was. She longed to know what at that moment was passing in his mind; in what manner he thought of her, and whether, in defiance of every thing, she was still dear to him.
Pemberley is everything that Elizabeth previously overlooked, all that Darcy is truly worth.