It was a vast dome, a hemisphere. Mainly blue in appearance but with patches of brown and green here and there and covered by great swirling masses of white that formed intricate spirals, great sweeping arcs and eddying waves, reminding the breathless questers of milk being stirred into blue coffee. The great patches of blue that covered the bulk of the dome were the shade of the purest, most perfect sapphire, fading darker to violet and indigo near the edges where the dome curved away from them. The very edge itself had the very slightest hint of fuzziness, as if it wasn’t quite in focus, where the indigo faded gently into the velvet blackness of the starry sky. The patches of green and brown spoiled its appearance a little, although most of those areas were hidden beneath the swirling white, but even they had a beauty of their own and soon Thomas found himself admiring the various shades of earthy tan and clay yellow, and even the occasional rare tint of brick red and metallic grey.

     They all stood transfixed by the sight for several minutes, none of them able to tear their eyes away from the awesome spectacle. “It’s the most beautiful thing I’ve ever seen,” whispered Lirenna, tears appearing at the corners of her eyes. “What is it?”

     “I’ve got no idea,” replied Shaun, equally awestruck. “I’ll bet it’s a complete sphere, though, with its bottom half hidden below the curve of the horizon.”

     “It would have to be huge to appear that big from such a distance,” protested Jerry, however. “Maybe a mile across.”

     “Yeah,” agreed the soldier. “What do you think, Tom?”

     “I’ve got no idea what it is either,” replied the wizard. “However, it seems likely that this room, and probably this whole complex, was designed for the sole purpose of observing it, probably using these lenses in some way. It must be pretty important if they wanted to keep a continuous watch on it, working in shifts to do it.” He turned his attention to the nearest lens and began cleaning some of the dust from it.

     “Can we get to it, do you think?” asked Lirenna eagerly. “If we found a way out of this place, could we walk over to it?”

     “I wouldn’t want to try walking across that landscape,” replied Matthew, indicating the jumbled boulders, jagged peaks and wide crevasses that waited for them outside. “You’d be lucky to get ten feet without breaking an ankle, or worse.”

     “Is it my imagination,” asked Diana, “or is it turning slowly?”

     They all stared at the vast, mysterious dome, and after a few moments they agreed that it was indeed turning, although very, very slowly so as to be barely noticeable. It was turning about its vertical axis, like a child’s spinning top, although on a colossal scale, as if it was a toy that belonged to the children of the Gods Themselves. What was more, the dome’s angle of illumination was turning as well, as though the yellow sun was orbiting it at exactly the same speed so as to keep the same side lit. No, that’s ridiculous, thought Shaun in outrage. The suns don’t move like that! Why, it would almost be more logical to imagine that both the dome and the yellow sun were standing still, and that we were moving around the dome, like the moons around Tharia. He shook his head in bafflement and decided to leave the solving of puzzles like that to those whose minds were better suited to it.

     Thomas, meanwhile, had managed to clean most of the dust from the lens and was looking through it. “I was wrong,” he admitted after a moment. “These aren’t for observing that dome, whatever it is. They’re some kind of scrying devices, like crystal balls. Look.”

     Diana, who was standing closest to him, bent to look through it and saw the same thing he’d seen; a wide expanse of forest seen from about half a mile up. As she watched, though, she saw something the wizard had missed. “The viewpoint of the observer is changing,” she said. “Dropping slowly down towards the horizon.”

     “What?” said Thomas, taking her place to look again. “You’re right,” he exclaimed a moment later, seeing that the angle of view was considerable shallower than it had been a moment before. “The difference is very small, but definitely noticeable. I’ve never seen any kind of scrying device that worked like that before. Normally, their point of view remains stationary unless they’ve been deliberately focused on a moving object.”

     “Let me see,” insisted Jerry, and the wizard moved aside for him, looking back up at the impossible dome. Like Shaun, he noticed the correlation between the turning of the dome and the movement of the yellow sun, and he puzzled over it for a few minutes as the others took turns to look through the lens. As he was looking, however, his attention was seized by the outline of one of the earthy brown areas, and he had the sense of some vastly important revelation, almost within his grasp if only he could concentrate his mind hard enough. Something about that outline. If only he could figure out where he’d seen it before...

     “Hey!” exclaimed Matthew suddenly, disturbing his train of thought. “The view just jumped!”

     “What do you mean, jumped?” demanded Jerry, squeezing up beside him to look into the lens as well.

     “I was rubbing the lens with my sleeve,” explained the young soldier, “trying to clean off a bit more dust so I could see better, but I must have pressed it a bit too hard. The lens moved a bit, and the scene in it changed.”

     “Let me see,” said Thomas, ushering them out of the way. They were right, he saw. Instead of a dense forest canopy, the scene now consisted of a wide grassy plain upon which a great herd of bison grazed, seen from almost directly above this time. “Hmm,” mused the wizard thoughtfully. “So changing the angle of the lens changes the scene it shows, eh?” He gripped the lens with both hands, applied a little pressure and twisted it around to a new angle, and sure enough the scene it showed changed yet again to show an expanse of wide, empty ocean in which the dark shapes of sea serpents and giant sharks moved with slow but deadly grace.

     “This is incredible!” exclaimed the wizard in delight. “It’s a bit stiff turning it, though.”

     “That’s probably what these are for,” said Jerry, indicating a series of handles and wheels lower down on the frame. He turned one, and the lens turned through a minute angle, almost too small to see, and as it did so the scene it showed sped past at great speed, as though they were flying over the ocean faster than any bird, or even a dragon.

     With a cry of delight, Thomas grabbed the handles and turned them this way and that, sending the point of view speeding crazily across the ocean, occasionally revealing a cluster of small islands or a vast raft of floating seaweed on which forests of palm trees grew. Now and again he would come across areas in which the surface of the ocean was hidden from view by a layer of clouds, indicating that the lens was looking down from a great height with the image magically magnified.

     “Hey, lemme have a go!” protested Jerry impatiently.

     Thomas was having much too much fun to stop, though. “There’s plenty more lenses,” he said, waving a hand in their general direction. “Go find your own to play with!” Grumbling to himself, the tiny nome did so.

     “This must have been an Agglemonian spying station,” mused Shaun thoughtfully. “From here, they could look down on all their enemies and see exactly what they were up to, giving them an enormous tactical advantage. No wonder they won so many of their wars back in the early days.”

     “But you can spy on your enemies using crystal balls or scrying mirrors,” pointed out Lirenna. “The introduction of a third method of scrying wouldn’t have had that much of an impact, surely, not when the first two methods were already so well established and widely used.”

     “Unless the lenses have some important advantage over crystal balls and mirrors,” said Jerry.

     “Such as what?” asked Shaun.

     “Well, with crystal balls and mirrors, it’s sometimes possible to tell that you’re being spied on,” said the tiny nome, continuing to clean dust from a lens as he spoke. “They have to create a magical construct near the scene or object being viewed which ‘sees’ it and transmits the image back to the ball or mirror, and that construct can sometimes be detected. What’s more, a clever wizard can use the construct to carry a magical attack back to the observer, using the same link that the observer was using to watch him with. Spying on a wizard with a crystal ball or a scrying mirror can be a very risky business.”

     “So?” said Shaun, who had only a vague idea what he was talking about.

     “Well,” continued Jerry, “What if these lenses work according to a completely different principle? What if they don’t need to create a magical construct at the other end?”

     Lirenna gasped. “Is that possible?” she asked in amazement.

     “I’ve got no idea,” confessed the tiny nome. “I’m just guessing.”

     “What would it mean if it were true?” asked Shaun.

     “Well, you’d be able to spy on all your enemies in complete safety and secrecy, with no chance at all of being discovered or struck back at. It’s what every strategist and tactician in the world’s been dreaming of for centuries. If the Agglemonians had it, no wonder they rose so quickly to rule the whole continent.”

     Shaun stared up at the ceiling with a dreamy look in his eye. “If that’s true,” he said, “then these lenses would be of enormous use to us against the Shads, perhaps even better than the Sword of Retribution. We’ve got to take one back with us. When Resalintas sees what it can do, he’ll be so pleased he’ll want to adopt us!” He grabbed the frame of the lens Thomas was using and tried to pull it, bringing a howl of protest from the wizard, but it was bolted securely to the floor.

     Lirenna had been thinking, though, and now shook her head doubtfully. “No, it doesn’t make sense,” she said. “If these things are so important, why were they abandoned here? Surely, as the Empire disintegrated and retreated, they’d have taken them with them.”

     “Who knows,” replied Jerry. “These things would have been the Empire’s biggest secret, in the beginning at least. Maybe everyone who knew about them were all gathered together in one place and all killed at once, so that no-one else knew they existed, or maybe they can’t be moved. Maybe something about the way they work means they can only be used from here, wherever here is. There could be any number of different reasons, we just don’t know.”

     Thomas, meanwhile, was trying to find Ilandia in the lens, to see how his homeland was faring in the war. He’d found a continental land mass and was speeding across it in the hope of finding something he recognised when he became aware of the same phenomenon Diana had noticed earlier. Originally, his point of view had been almost directly overhead, so that he was looking vertically downwards onto a monster-infested ocean, but as he moved his point of view further and further westwards (he called it westwards, although in truth he had no idea what compass direction it was), his point of view was moving further and further away from the vertical so that he was looking down on the shrubby, hilly countryside from an ever shallower angle. Eventually, the horizon itself came into view and now he noticed something even stranger. Even though he was no longer touching the handles that moved the lens, and even though the scene seen in the lens was stationary, the angle at which he was viewing it continued to grow shallower, losing all sense of depth, and shrinking as well as though it were moving further away. Eventually it was so close to the horizon that it was lost in the haze. What in the name of the Gods is going on? thought the wizard in bafflement.

     On an impulse, he turned the wheel a little more, turning the lens a tiny fraction to the right, and the image it showed was raised a little so that he was looking higher into the sky. A thin ribbon of pale blue sky followed the horizon, darkening with height to violet and indigo with banded layers of high altitude haze until he was looking at starry night sky.

     He turned the lens back the other way, and the land came back into view after he’d once again passed through the shimmering layers of atmosphere that veiled it. He looked up from the lens, his head spinning in confusion, and found himself looking out through the room’s long window at the mysterious, beautiful blue and white dome that sat on the jagged, rocky skyline. He stared at it with bulging, staring eyes as an explosion seemed to go off inside his head.