Cyclopean

Built from or relating to an ancient masonry made up of no mortar and giant irregular blocks.

According to Webster’s, the name comes from the architecture in ancient sites like Troy and Mycenae where the design was so puzzling that it was suggested that only a race of Cyclops could have such strength to build this.

The word features prominently to describe the architecture of the fictional city of R’lyeh, resting place of Cthulhu.  The angles of the city were said to make no sense.