New York City, USA

New York City outpaces #10 Istanbul for architectural density, with every decade of the 20th century preserved across Manhattan's 23 square miles. Its skyline, the most recognizable on Earth, showcases steel, limestone, glass, and brick in a 150-year continuous building boom. More than 20% of Manhattan's buildings were constructed before 1920, offering a living timeline of skyscraper evolution. The Hudson Yards development and the rebuilt World Trade Center demonstrate modern ambition, while the High Line's transformation of a 1.45-mile elevated rail line into a park redefines urban reuse. No other city on this list matches New York's sheer concentration of landmarked structures, with over 1,400 individually designated landmarks citywide.