references:

• ...the tap glowed with a brilliant white light and began to spin. Next second, the sink began to move; the sink, in fact, sank, right out of sight, leaving a large pipe exposed, a pipe wide enough for a man to slide into.
• It was like rushing down an endless, slimy, dark hole. He could see more pipes branching off in all directions, but none as large as theirs, which twisted and turned, sloping steeply downward, andhe kne wthat he was falling deeper below the school thatn even the dungeons...and then...the pipe leveled out, and he shot out of the end with a wet thud, landing on the damp floor of a dark stone tunnel large enough to stand in.
• ...[T]he tunnel was quiet as the grave, and the first unexpected sound they heard was a loud crunch as Ron stepped on what turned out to be a rat's skull.
• The light slid over a gigantic snake skin, of a vivid, poisonous green, lying curled and empty across the tunnel floor.
• The tunnel turned and turned again...He wanted the tunnel to end, yet dreaded what he'd find when it did. And then, at last, as he crept around yet another end, he saw a solid wall ahead on which two entwined serpents were carved, their eyes set with great, glinting emeralds...The serpents parted as the wall cracked open, the halves slid smoothly out of sight, and Harry...walked inside.
• He was standing at the end of a very long, dimly lit chamber. Towering stone pillars entwined with more carved serpents rose to support a ceiling lost in darkness., casting long, black shadows throught he odd, greenish gloom that filled the place.

As he drew level with the last pair of pillars, a statue high as the Chamber itself loomed into view, standing against the back wall...it was ancient and monkeyish, with a long thin beard that fell almost to the bottom of the wizard's sweeping stone robes, where two enormous gray feet stood on the smooth Chamber floor.