30 St. Mary Axe
Why It’s Cool: In recent years, London kept a somewhat low architectural profile, but the buildings it did add—like this glittering office tower, nicknamed “the Gherkin” for its cucumber dimensions—exude panache. Diagonally striped bands of two shades of blue run almost the length of St. Mary’s 41 stories, which taper to a point. The triangular panes, of some 260,000 square feet of glass, form a captivating one-of-a-kind mosaic. And workers can crank them open for breezes, which wins this edifice points for greenness, too.
How to Visit: The spire’s white-tablecloth eatery is open only to those who work onsite. However, anyone can drink a toast to architecture in the first-floor bar.