Cathedral of Saints Peter and Paul, Saint Petersburg, Russia

The foundations for a citadel and the original wooden church were laid in 1703 but over the centuries the construction expanded to create a Cathedral and fortress with the Mint, garrisons, prison cells and the Senate being added later, creating the vast construction that we see today. The vault is the resting place for Russian Emperors and the fortress houses museums. Location: Petropavlovskaya krepost, 3.