Despite the orderly pattern of studs on LEGO parts, those round studs are the key to building large structures that include curves, look organic, or even embrace chaos. The family of techniques that allow construction of curved walls with simple round and rectangular LEGO elements opened my eyes to the possibilities of this hobby. I was at my first LEGO convention, BrickFair Virginia 2015, when I spotted this technique in use. It's fairly common and by no means new, but it was new to me. It was a pivotal event in my transition into an Adult Fan of Lego (AFOL) and has captivated me ever since. I've used it in plenty of my own creations, and spotted it everywhere, including LEGOLAND.
this round-walled lighthouse is at LEGOLAND California
saw this at BrickFair, from builder Mark W.
Simply put, when a stack of bricks is held together by a column of round studs, those studs can act as a hinge. All that stops it are those pesky corners you find on most LEGO elements.
The easiest way to remove the corners is to leave gaps, and that means using something a little longer than a 1x2.
Every column of bricks is now freed from the orthogonal grid, and can be positioned across a wide range of angles with respect to its neighbors, from jarring zigzags to graceful curves.
The caveat is that the resultant walls are latticework. While providing handy footholds for adventurous climbers of either the plant or animal variety, the resemblance to common masonry is minimal.
Fortunately, LEGO makes rounded elements. In fact, they started doing so way back in 1955, three years before they settled on the modern form of the classic 2x4 brick. One of the first round elements made was also LEGO's smallest part at the time: a 1x1 round brick.
In its early form, this element lacked the bottom lip found on the modern version, make it easier to build clean, smooth columns but a bit more difficult to separate one from the stack. For a while after the first redesign, it retained the solid stud. Switching to hollow studs created an attachment point for 3.18mm bars while also reducing the choking hazard for the youngest Lego fans.
Regardless of the design variant, these round bricks are functionally identical when stacking them in walls, and perfectly sized for filling the holes in the 1x3 lattice. Not only that, but their rounded shape conveniently stays out of the way of the pesky corners of adjacent rectangular brick, allowing flexible walls to retain an impressive range of motion.
Circles are the logical extension of curves, and once you have enough bricks to close the loop, you can add to the circumference as much as you wish in 4-stud increments. Unfortunately, using this pattern you can't make the diameter much smaller than 24 studs without rudely intruding on the designed tolerances of your elements. Fortunately, there are lot more elements to choose from.
LEGO has a few round parts which are a bit narrower than a 1x1, and swapping these into your structure is another way to build smaller round shapes.
In the last few years, LEGO has introduced 1x plates with rounded ends. These allow the maximum flexibility. Having SO many degrees of freedom creates all sorts of new opportunities, but makes it harder to create smooth, constant radius structures. But sometimes you want crazy flexible shapes, and with LEGO, there's always a way!