With modern technology, we could probably take any building and through regular maintenance, keep it forever. On the other hand, we have weapons that can vaporize any man-made structure in an instant.
It is more about how significant it will be in the future, and we don't know. Maybe some random university building will be preserved for centuries because that's where the cure for cancer will be found. Maybe ITER, if it delivers on its promises, it will be of great historical significance, and maybe a bit radioactive. Maybe an airport or train station being built today that will become a major trade hub. An office building that miraculously survives a nuclear war. Some ugly structure that will be seen by generations as the most representative of 21th century art. Anything, really.