Basically the whole city is a 100 feet in diameter cylinder about 40 feet thick carved whole from a mountainside. The entire cylinder was wrapped in a gigantic tinsel net. This net was then had the 'adamant' spell cast upon it. The purpose of the adamant net is to force the cylinder to maintain its structural integrity rather than break.
Three holes were drilled into the surface of the rock. Each hole is 25 feet from the center of the rock and spaced equidistance around the rock: (picture). These holes are about 10 feet in diameter.
At the bottom of each of these holes are four other holes spreading out a few feet from the holes. These holes are 1.5 inches in diameter. Into these holes glass rods were inserted and then adamant-ed.
This setup provides the basic structure upon which the entire rock is held.
Now the floating part... The rock is suspended by adamant chains that extend upward, through otherworld portals and are moored to a planets surface (using 10 yard screws) on the other side of the portal.
The portals were cast in such a way that as you go upward through the portal you end up going downward on the other-side. Originally we had intended three separate worlds. But pure fluke of nature was that one of the portals was a near vacuum so had to be abandoned. As such two of the portals connect to the same world, just opposite sides. All worlds are barren by definition.
The rock is then hauled into position where the portal is actually inside the rock. A large creature was then tossed into the hole and blue fielded. Then the hole was filled in with mortar. So that nothing on this side of the portal could target the portal or shut it down.
Once all the construction work was done. A solid night's work. The first dwellings (high rent apartments and a hotel) and shops were constructed. Its left up to whoever wants to come up to figure out how to get there. No allowances were made for waste at all. Its assumed they are tossed over the side or onto the rock where rain will wash refuse over. Anyone actually caught tossing objects off the side is thrown off.
What started as a conceptualizing problem in magichanics is now the biggest attraction in Rougtero. The Floating City of Rougtero is unique and adds some actual value to an otherwise dull city.