Recently, I had to re-install a Minecraft server that is hosted remotely. I backed up the "world" folder to my computer before doing the reinstall. Now that the server has been reinstalled, I have copied the world folder back to the server and have been unable to find the massive city that I have built.
Is it gone forever? Or did I forget to back something up? Me and a team of 3 other players have been in creative mode searching the map for hours but have been unable to find anything. I have tried dynmap and essentials plugins to help aid with the search. I also made sure that the Minecraft config file was set to match the name of the world folder. The only difference that I see with the server installation is that this time it's running version 1.8.8. Before the re-installation, the server was running version 1.8.3, but I don't know if that makes any difference.
You could try downloading McEdit (I reccomend a 1.3.x version as the 1.4.x versions have been crashing a lot for me) and opening the level.dat of the backup. Then, switch to chunk view with tab, and use right click to drag the world around, looking for anything irregular that might be your city. If you look at all the generated chunks and don't see anything, then you probably made a mistake during the backup process, or a mistake in putting it back, in which case I suggest ensuring that the world name in properties exactly matches the backup name.
Being a server owner, I can completely understand. Now, there is two things that may have happened. Number one being, you could have downloaded a "blank copy" of your world. This has happened to me plenty of times. It is when your backup you download downloads the chunks, but fills them in with seed data upon first boot. Sadly, if this has happened, your world is gone. If you are going to update your server, I HIGHLY recommend that you use multiverse to make a secure clone. the /mv clone WORLDNAME BACKUPWORLDNAME command to fix this. Other than that, you might just be screwed. Sorry.