It's still highly used in the EDA industry - almost every EDA tool is scriptable with Tcl. There are even IEEE formats that are actually Tcl dialects, e.g. UPF (Unified Power Format) for describing power related features of circuits.
I wonder if the distinction of SubLists and SimpleLists makes static code analysis and syntax highlighting more viable than in Tcl where you cant distinguish between "code" and "data"...
Here's the French castle building project in Guédelon: http://www.guedelon.fr/en/
Since 1997, they are constructing a castle from the grounds up using medieval techniques. Quite impressive...
Airports are actually pretty nice, when looking at them from above. The way their geometries are embedded into different landscapes is sometimes quite intriguing.
See https://airports.flopp.net/ for some random examples.