You never know what's underneath, but that building was supposed to be an example of NK's power in the region. At the same time it was started, huge skyscrapers in Dubai, Thailand, and China were all beginning construction. The reason theirs is super wide on the bottom has to do with their poor quality steel and low grade engineering and construction processes - in an earthquake zone. Possibly also so it can serve some military purpose: pyramid designs are stable. It still isn't finished a decade after it was supposed to be,, and sits half empty. Apparently there is a functioning hotel on a few floors. The Thailand skyscraper isn't full either, but at least it's finished.