1 of a kind jobs

Was just reading about the Svalbard seed vault and got me thinking about how they build stuff in such a remote area. Any body on here been apart of some obscure 1 of a kind jobs similar to that. For me when I was greener than green worked on the SU green data center which at the time was the most efficient building of its kind in the world. Wish I could do it again so I could understand how unique the build was mechanically.