There are eight levels, and the last two are filled with water:

Some background for the races can be found in the Settings section - both in the History and on the individual Race pages. There isn't a lot, and I'd very much want this section to grow. There's some neat information waiting to be released :]
Not all the cities in Yliakum have names yet, so it's hard to get down to such a level of detail. We'll all have to make do as best as we can while we wait for the game to expand. As long as you're not doing anything outrageous - creating massive sky-cities for example - you're free to populate the world with little towns or villages here and there. It's really unavoidable at this stage. Just have to keep in mind that once the world grows, your RP will have to adapt.
There is a lot of cool stuff in our Q&A sessions (and we're lagging behind again this month :<) but you can find a good three months worth of setting questions and answers
here.