An 1831 book said that if you pass under one of these, you must spit through it or spit three times afterward; what is it?

Which company trades under the stock symbol AMZN? An 1829 visit to Holyrood Palace in which city inspired Mendelssohn's "Scottish" Symphony? In which month of 1830 did the French revolution that toppled King Charles X break out? An 1830s painting by Karl Briullov depicts the last day of which city before a volcano destroyed it? An 1833 meteor shower is why which state's license plates once said "Stars Fell on"? An 1837 fire destroyed the Winter Palace in which city, though the Hermitage's treasures were saved? Which 1845 Richard Wagner opera centers on a song contest at the Wartburg? Hector Berlioz's 1846 work "The Damnation of ___," based on Goethe, is about which man?