The narrow, round tunnel was damp and winding, with faint trickles of water echoing off the stone walls.
Following the faint light of their wands, the four of them moved quickly through the corridor until they emerged into a towering stone passageway.
Now, finally on the main path, they still had quite a ways to go to reach Hogsmeade.
This was William's first time using this particular passage, which the twins claimed had a mysterious grandeur worth seeing.
Though usually he took a different route, he couldn't help but be curious now that he was here.
But when they stepped into the expansive passageway, William quickly realized exactly where they were.
The architectural books Dumbledore had recommended had mentioned this underground complex.
One line in particular had stayed with him: "Rowena Ravenclaw's daughter, Helena, once became lost down here and nearly didn't return." Afterwards, Godric Gryffindor had sealed it with enchantments, and the entrance was lost.
Apparently, though, the Marauders had discovered this entrance and even worked out the password.
It didn't feel like a mere passage—it felt like they had stepped into the fabled catacombs of Hogwarts itself.
The main path was bordered with smaller chambers and side corridors, all connected in an elaborate maze of grand stone pillars and shadowy alcoves.
In this massive underground vault, one could easily get lost without the aid of the Marauder's Map, which thankfully showed a clear route leading straight to Hogsmeade.
They pressed on, weaving deeper and deeper into the castle's underbelly. With each step, William's heart raced a little faster.
Their path led them through an increasingly complex layout, with twists and turns that made the stairways of Hogwarts look simple in comparison.
Eventually, they reached a wide corridor lined with massive marble columns that led them into a large, circular chamber.
Here, the air was dense and thick, and William had to shake off the faint sense of claustrophobia as his footsteps echoed in the empty space. The ceiling here was low, and faint ceiling lights flickered to life, illuminating rows of Doric columns that reminded him of ancient temples.
The structure was achingly familiar, after a moment, he realized he was looking at a replica of the Parthenon.
It had the same design as the famous Greek temple, a colonnade around a rectangular inner chamber, albeit without the signs of age and erosion he would have expected from ancient architecture.
The sculptures and engravings on the columns were clear and unweathered, with intricately detailed runes carved into each.
William's attention was so captured that he almost didn't hear Fred when he said;
"Oh, this is nothing, William—just wait until you see what's next." Smirking, Fred darted left, leading them through the maze of columns and down yet another wide hall.
As they passed various statues and artifacts, they came across a model of Hogwarts Castle that was strikingly similar to the wooden one Dumbledore had gifted him, though this one was crafted from solid gold and sparkled in the torchlight.
Then William heard it—a soft rushing sound like water.
They emerged in front of an underground lake.
In the middle of the lake stood a small island, occupied by a single two-story building of smooth granite that gleamed under the dim lights.
It was a pyramid.
Only it wasn't a complete pyramid—there was no peak. At the top, there was a large, flat platform where four ornately coloured sarcophagi lay, each a different hue.
"How's that for a view?" George grinned, looking at William with a triumphant expression.
"We were stunned when we found it," Fred admitted. "Who'd have thought Hogwarts had something like this buried deep below the castle?"
Cedric stepped closer to the lake, but was stopped by an invisible barrier that rippled faintly before him.
"There's a protective spell around it," Fred explained with a shrug. "We can't cross over to the island."
"Whose coffins do you think those are?" Cedric wondered aloud.
"Could they belong to the Founders?" William mused, an idea forming.
Only the Founders could have authorized such an impressive structure within the castle grounds.
"Possibly," Cedric replied, his tone reflective. "But I doubt their bodies are actually in there. I read that all of the Founders except Helga Hufflepuff eventually left Hogwarts."
A chill wind swept through the chamber, and as they stared at the tombs, a shiver ran down their spines. They quickly turned to leave, missing the slight tremor that shook the golden compass resting by the lake's edge.
Hastening their pace, they exited the main vault and entered a long, narrow hallway lined with doors, each marked with a different number.
"Do you think we can open any of these?" Cedric asked excitedly.
"Every door's locked," Fred replied with a resigned shrug.
William pointed his wand at a nearby door, muttering, "Alohomora!" But the door didn't budge.
He then retrieved a small knife from his pocket—the same one the twins had given him—and ran it along the crack between the door and the wall. The blade glowed faintly, but it left no mark, and as he withdrew it, he saw that it had partially melted from the attempt.
"Maybe we should find some Muggle explosives," George suggested with a sigh.
William rolled his eyes. "And where exactly would we get that?"
George looked crestfallen. For anyone interested in exploring Hogwarts' secrets, facing an impenetrable door was more than a little frustrating.
"We should keep moving to Hogsmeade," William said at last.
With no way to access the locked doors, they continued down the passage, enjoying the view of mysterious artifacts and architectural marvels as they passed.
But soon, their enthusiasm turned to weariness, and they trudged forward, motivated only by the thought of Honeydukes' sweets awaiting them.
About forty minutes later, the corridor sloped sharply upward.
"Almost there," George said, pointing to the winding stairway that spiraled upward out of sight.
But just then, William paused, straining to hear something faint.
"Did you hear that?" he whispered.
"What?" Fred asked, looking around.
"It sounds like something's moving," William replied, brow furrowed.
He held his breath, listening intently. The sound was faint—muffled by the thick walls. It was impossible to tell if it came from far away or just around the next bend.
Could it be that they weren't alone in the catacombs?
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