Over on the east side of Dallas is a home made out of a Nike Missle Silo. Dallas had one of the few defense missle bases designed to repel bomber attack. (The idea was to launch nuclear missles that would give an airburst to wipe out waves of attacking aircraft. The logic of protecting a city in the middle of the U.S. as opposed to east/west coast is curious, but that's politicians.) The silo complex was purchased and turned into a multi-level underground home.
I would love to appraise it but it would be at my price, not subject to any guidelines and not subject to any time frame for completion.
The cost approach would be a treat in itself with estimated costs and functional obsolescence.
If one has the time (and the client has the money) these can be a challenge.
I remember doing two "cottages" on Mackinac Island about 5 years ago. They turned out to be cedar log houses of 2200 and 2400 SF with moss chinking on cedar foundations, about 80 years old, no central heat, water from the lake (summer only-it froze in winter), and on leased state-owned land. I earned my pay on that one but I learned a lot about possessary interest and about the goings-on on the Island.
We had those sites in Chicago as well. We just moved in to a new building out in Barrington / Palatine (for the day job) that was built on some old government land that used to have a silo complex. They also had to move an old cemetery so everyone keeps wondering about old disgarded warheads and caskets popping up through someones cube.
Here's a link to some good shots of some of the Nike sites on the lakeshore.