Complex sentence: One of the most significant monuments is that to Major General John E. Wool, a monolithic obelisk weighing, a technological achievement of its time that is surpassed in weight only by Cleopatra's Needle in New York City's Central Park.
Split into simpler sentences: One of the most significant monuments is that to Major General John E. Wool. The monolithic obelisk which was a technological achievement of its time is surpassed in weight only by Cleopatra's Needle in New York City's Central Park.