I swung by the Basilica of the National Shrine of the Immaculate Conception because the pics looked pretty on Pinterest and I was in a mood to explore. That's all the motivation I need sometimes.  It's the largest Catholic church in North America and the tallest inhabitable building in DC.  It took 40 years to build, 1921-1960, and receives around one million visitors per year. Popes John Paul II and Benedict XVI have both stopped by.