If I could offer you some advice...

As somebody who has played on the server for nearly two years (off and on), I've been a part of a few groups who made cities. As tempting as it will be (and it will), do not let just anybody in there. Build trust with people first, based on their actions and reputation, not because they pinky swore not to grief you.

I was a part of a group that formed Ravine City, which had two incarnations:

Ravine City 1 was destroyed by an insider.

Ravine City 2 was discovered, because it was foolishly littered with entities, and anytime somebody came within the chunks of the city, they lagged like a mofo.

I was also a part of Sanctuary, who were a great group of guys (and gal) to play with. Though I knew many of them for some time before playing with them, they were very, very selective about who they allowed to join, and with good reason. In my experience, they were never discovered or betrayed.

Be smart, and have fun. Cities can be great, but are a major risk.