The two things I enjoyed building the most were bridges and towers. I was fascinated at how many bricks that didn't even come close to spanning a gap could be fastened together in such a way that the gap could not only be spanned, but carry a load as well. I was also fasinated at how bricks could be attached one on top of the next to build very tall structures.
This tower I built when I was probably 13 or 14. There are actually two towers here. The smaller one that lookes striped like a candy cane is made out of older Lego bricks that seemed to be a bit more washed out than the newer bricks. I didn't want to mix them with the newer bricks, so I used them to build this tower. The taller tower is color coordinated, using all the bricks of a certain color before starting to use the next color. The tower was topped with an antenna that was barely a fingernail's width from the ceiling. The tower was rather unstable, and it did fall over a few times, sending Lego bricks throughout the room. At the base of these two towers, an entire Legoland town grew, complete with fire and police, hotel and car fixit shop. There was even a railroad and an airport.
I built the bridge when I was younger. It was my first bridge made of Lego bricks. Using two road base plates, it spanned a gap between a foot stool and the box I kept my Lego bricks in.
Probably not long after the Giants victory, I started construction on the longest Lego brick bridge I have constructed yet. Originally, this bridge held Lego railroad tracks on the top layer, and HO gauge tracks on the bottom layer. As I never found a use for the bridge to carry actual Lego trains, I reconstructed the top layer to carry a second HO gauge track. I have yet to find a use for the bridge to carry HO trains across a gap either.
That's just one tower of the bridge, holding up the "suspension cables", and you can see them start up to the second tower to the far left of the picture. The "cables" turned out to be more of a liability than to provide actual support, but they looked nice. The bridge was strong enough to be held with one support under each tower while a train passed across. Those are HO gauge box cars in front of the bridge.
When I was in college, one of my roomates brought all of his Lego bricks to college after we discovered that we both had Legos. I used practically all of them in this tower that again reached within a few fingernail widths of the ceiling. Yes, those are lego people perched on the building. One is taking a coffee break, another is about to jump out of frustration over small office space, another is an astronaut, and yet another is reparing an antenna. Perhaps one is washing windows.
We also managed to string Christmas lights most of the way up the tower. There was a fire escape that went part way up the side of the tower. This provided an escape route for when the tower was about to fall over... which happened frequently.
Later in my college life, I built a much stronger tower. I don't have a picture of it online yet.
Large Lego Bridge
Late in 2010, I began construction of a lego bridge that would reach across a gap in a book case large enough to hold a TV!
To build the bridge, I built the side supports first, then placed the arch on top of them. Then I placed the main deck on top of that. I had many trials building this bridge including the arch falling apart until I had built it strong enough to stay together while I put it into place, and discovering the gap was a tiny fraction narrower than a whole number of 1/1 bricks.
Here is the YouTube video showing how I put the arch in place.
Here are some pictures of the finished bridge.