Images NL Architects
The Port of Rotterdam ran a competition for the design of a 70 meter (230 feet) high tower for a radar and observation platform. Designboom shows NL Architects' proposal to build it out of shipping containers, an appropriate choice for one of the world's busiest container ports.
They originally wanted it to be one container thick, but did the math and determined it wouldn't be stable enough, so they doubled them up. It would still need reinforcing to stack 25 containers high, especially given that it was going to have an elevator and stair inside.
Unfortunately the project was cancelled because it would not be dramatic enough; Designboom writes that "that the neighboring new generation wind turbines by their sheer size would dwarf any landmark."
More at Designboom
Too bad, it would have been a lot taller than the Freitag Recycled Shipping Container Store in Zurich.
And perhaps more stable.