Found it!

Okay, I found the corresponding Lovecraft excerpt to my Grabkapelle experience:

"At last he saw the tower plain against the southwest, and a huge stone bulk rose darkly at the end of an alley. Presently he stood in a wind-swept open square, quaintly cobblestoned, with a high bank wall on the farther side. This was the end of his quest; for upon the wide, iron-railed, weed-grown plateau which the wall supported- a separate, lesser world raised fully six feet above the surrounding streets- there stood a grim, titan bulk whose identity, despite Blake's new perspective, was beyond dispute.

The vacant church was in a state of great decrepitude. Some of the high stone buttresses had fallen, and several delicate finials lay half lost among the brown, neglected weeds and grasses. The sooty Gothic windows were largely unbroken, though many of the stone mullions were missing. Blake wondered how the obscurely painted panes could have survived so well, in view of the known habits of small boys the world over. The massive doors were intact and tightly closed. Around the top of the bank wall, fully enclosing the grounds, was a rusty iron fence whose gate- at the head of a flight of steps from the square- was visibly padlocked. The path from the gate to the building was completely overgrown. Desolation and decay hung like a pall above the place, and in the birdless eaves and black, ivyless walls Blake felt a touch of the dimly sinister beyond his power to define."

-HP Lovecraft, "The Haunter of the Dark"