Scale model of the Gate way arch/ Scale is 1/500 for the outside profile. The thickness is scaled up from that by 2.5 to make a good block toy. THe outside curve is a "weighted catenary). The equation of the outside curve is at full scale is : y(x) = -A*cosh(x/A) + B. A = 101.47. B = 716.77. There are 17 blocks and five base pieces. It is slightly tricky to assemble, but is stable after assembly. Something here for all ages.

Print. Snap together the base. The bottom blocks fits to the base with tow bosses on the base fitting two holes in each base block. The holes are too small. I used a tapered reamer to get a precision fit to snap the bottom block onto the base. One way to assemble is to stack up each side ah high as you can without it falling over. The assemble the remaining blocks and carefully place these on on leg and then the other. Trickey but not too hard.

Attribution - Creative Commons

GatewayArch, BlockToy, Architecture, StLouis, Catenary