I like to think of myself as a builder... when in reality I'm more of a gatherer/explorer.
When it comes to building, I built a floating city out on the middle of the ocean. The foundation being made from Smooth Stone 1/2 Slabs, and the corners being whole Smooth Stone Slabs. There was even a fountain as the town square. Aside from the center of town, there was a floating garden, town mine that went down to below sea level... and into an abandoned mine, and a 50x50 jungle tree/monster farm. (The monster farm was an accident but the 12 levels a night was reason enough to keep it)
I'm an oddball that decides that building down on the surface of the ocean is a good idea, aside from needing at least 27 trips with 15 buckets, which I used for cascading water effects. Probably my own personal favorite was the Neapolitan bridge, which consisted of jungle (pink), white oak, and that dark brown one... I never was good at the wood names.