Gravelight by Marion Zimmer Bradley

decades before that, and it certainly seemed to have been abandoned since the fire.
    He shook his head. There could be a dozen prosaic explanations for the bare earth, including an antique insecticide spill. He pushed aside his speculations, and with them any acknowledgment of potential danger. He wondered how much of the inside was left.
    Wycherly circled the building, choosing his footing carefully. The curving drive had led up to a front entrance reached by a grand terraced staircase. The stairs and their balustrades were still there, although the closer he got to the top, the more the stonework showed the effects of that long-ago fire. Finally he reached the last step. The archway through which a long-ago patron would have entered remained, as did a part of the wall.

    There was nothing else.
    Wycherly stood on the last step and gazed down, fascinated. The floor plan of the house remained, printed on the earth, but the years and the fire had left nothing behind but the house’s shell. The upper stories had caved in and burnt to ashes, and where there had been cellars, those too stood exposed, opening a chasm three stories deep beneath his feet. Below the level of the sheltering earth the outer walls were intact; he could see the decades-old bricks and mortar, and everything was laid out in such a neat regular fashion—all straight lines and right angles and cubes—that he’d only been staring at it for several minutes when the thing that didn’t fit caught his eye.
    It was a black stone staircase running down along the left-hand wall. It began at what had once been ground level and made a gentle curve out into the main part of the cellar, running from nowhere to nowhere. When Wycherly’s eyes had adjusted fully he realized that the staircase ended below the basement level. He wondered where it led, and why.
    It did not occur to him that no one knew where he was; that a fall could leave him trapped and helpless. He felt the same irresistible glee that he had always felt when he stumbled on someone else’s secrets: that the secrets here belonged to long-dead strangers made no difference.
    Wycherly circled the building until he reached the black stairs. They were marble, and might once have even been ornate, though they seemed to begin below the levels of the public rooms. Another oddity in a sanatorium that seemed to have been erected by eccentric plutocrats. There was a landing two-thirds of the way down the black stairs, and after that, one last short flight would take him below the sub-cellar.
    Wycherly started downward. The walls of the sub-sub-basement seemed to close in on him as he descended; he looked back the way he had come, and the far-off daylight was cool and dim. He could escape easily. He was perfectly safe.
    So Wycherly told himself, but it was with a certain reluctance
that he stepped off the bottom step, onto the floor. It was smooth and flat and dark: a close-grained stone like basalt or even sandstone, covered with fallen leaves, ancient cinders, and blown dust. The surface made for slippery footing.
    The walls were rougher than the floor, and bore the marks of the hammers and chisels that had sculpted them out of the living rock. He could still see the marks where the bolts anchoring some framing or wallcovering had been sunk, though the paneling had gone to dust and ash as if centuries, and not mere decades, had passed.
    Walking gingerly across the floor, Wycherly felt a sensation of weight, of depth—though logically there was no way for him to be able to sense such things. He looked around, trying to distract himself from the sense of claustrophobic pressure that being here gave him.
    The room was …
    Wycherly frowned, peering into the gloom. To tell the truth, he couldn’t tell exactly how big the room was, or even its shape. A phrase from an old book he’d read once came back to him: non-Euclidean geometries. Maybe the architect had been drunk when he