Magic Bottles
Bottles are magical items that are bigger on the inside than on the outside. Rings bound specifically to certain bottles allow the user to enter and exit that bottle by wearing the ring and twisting it. On the inside, bottles have many floors with the layout exactly matching the exterior layout of the bottle; for example, the first few floors at the neck of the bottle are small, but then get bigger as you move down towards the main body of the bottle. No external light makes its way into the bottle, instead it is lit by the dull glow of its walls (glowing whatever color the bottle is) and whatever man-made light sources are inside. The air is stale and completely still, as outside air is unable to penetrate the bottle, but it does not seem possible to suffocate in it. Bottles are often use to transport troops, goods or even nobles, as the weight and size of matter in the bottle does not actually affect its external physical properties. Although a ring is needed to enter and exit the bottle, the wearer of a ring can touch other people/objects as he's twisting the ring to bring them inside or outside. The limit to this is roughly 50 people at a time, or 10 horses at one time, although horses have difficulty managing the stairwells and must stay on the smaller upper floors. Bottles have drop-holes for the disposal of waste, which magically transport objects to points on certain wizard towers, above fire dykes.