I've noticed a number of different varieties of unusual forests, though mostly they're repurposed, and stand above or on the ground, rather than the one seen in the image below, where the trees are inverted like roots. There's the massive forest that we see every day in the United States, the backbone of our digital culture is strung along the carcasses of dead trees, wires and cables hanging from tree corpses, an enormous chunk of our social interaction and economy dangling above us, moved by the wind and rain. Then of course there's neat and orderly forest, forests that have been cut down, stripped, and the elements stacked in sequences so that people could live inside of them. There are stockade fences, and picket fences. There are old roads from Colonial times and into the 19th century there were made sections of felled trees, and then others that were made from milled lumber (as in Plank Roads). There are forests that have been cut, and then milled all to one size, and laid next to one another in parallels and connected with heavy steel ribbons that stretched for hundreds of thousands of miles, their enterprises given ironic and commodious names with words like "Atlantic" and "Pacific" in them (like the "Union Pacific Railroad"). Dead Wood is everywhere, some of which was simply cut down, stacked, and then slowly burned.
Before being replaced by steel, foundations like this were made of lumber and/or stone, and was hardly uncommon–what is uncommon, to me at least, was to see a picture of finished footings, and then to be given such a creative name like "inverted forest". But this is what they were, as we can see here in the New York World's Fair Bulletin in 1937: 11 miles of forests pounded into the soil to support the weight of the iconic Trylon.
The Trylon is the spire in the middle of the image, next to the sphere–they were both enormous. The spire rose some 600', while the sphere was 180' in diameter–both were gone by 1941, razed at the end of the Fair (1939-1940), their materials used for the war effort. Both stood on the inverted forest.
[From a private collection, via the Library of Congress, from the White House in 1938.]
In the Alphabet of Inverted Things, forests may be the most unusual: inverted chords, melodies, voices, pyramids, river deltas, microscopes, personality. Forests seem so awful in their way. Inverted.