I joined skill4life's server, a minicity on Slopes. He had pre-made brick terrain for the city, and was expanding it. I claimed some area on or behind a hill or something. It was pretty small in total. I made roads and a little bridge and stuck my
green pixel xC3110x logo on a hill. I thought his skyscrapers were impressive (I think they consisted of alternating opaque/transparent plates...)
I also remember the first place I joined on Roblox. I think you were supposed to build your own go-kart and ride it down a track, but there were bricks strewn everywhere, I had no idea how to move anything and I kept getting killed by random explosions.