I used to play a ton of minecraft years ago. All I wanted to build was skyscrapers. It was a huge PITA though. I ran a server with tons of mods (who remember's bukkit? That was the best / last of the mods I used) but still with the height limit at 127 blocks and ground being about half that, scyscrapers weren't easy.
Here's a shot of the city we had started building. That tan / blue building was inspired by 60 Wall St. It featured an 8 story underground gold vault. The big white block is a pretty sweet performing arts theater. Also, under water / ground we had an elaborate city accessible through the base of that tower at the end. That golden domed building was a central train station which access the full subway system that ran around the map. The Burj Al Arab is on the island to the right. The brick building was a library. The building in the bottom right was Wayne Manor.
Also, since you couldn't go to the nether back then in multiplayer, we actually recreated a HUGE swath of nether underneath the water to the right of that picture. The entrance was from the aforementioned underground city. It was pretty crazy. We started building a post-apocalyptic city in there too. Not pictured to the right of the shot was a walled medieval city that featured a hotel, garment shop, tavern, and royal chambers.
All of this was about a month's worth of work for 3-4 people.
