What is the underlying meaning of "Whited Sepulchre"?

Question: What is the underlying meaning of "Whited Sepulchre"?

Or, what is the symbolic significance of "Whited Sepulchre" in Heart of Darkness?

Ans. The metaphor “Whited Sepulchre” refers to Brussels, the location of the headquarters of the ivory-trading Company that employs Marlow. The Company’s headquarters is situated not in London but on the continent, in a city that Marlow declares “always makes (him) think of a ‘whited sepulchre.’” That the Company could just as well be operating from the British capital as from this particular city is suggested by the fact that the story is being told aboard a boat moored off a place called Gravesend.

The term “Whited Sepulchre” is drawn from Christ’s words in St. Matthew’s Gospel (23:27), used to describe those who are not what they seem—hypocrites who disguise their moral corruption with outward shows of virtue: “…like whited sepulchres, which indeed appear beautiful outward, but are within full of dead men’s bones and of all uncleanness.”

The powerful image of a whited sepulchre entombing dead men’s bones symbolically reflects the theme of economic exploitation. It serves as a biting criticism of the trading company—a band of modern Christian “pilgrims”—portrayed as contemptible hypocrites who, in their “vile scramble for loot,” leave death and desolation in their wake.