10. The Crusades Ruined Everything
Various crusades had been raging throughout the Middle East for some time, but it was the fourth crusade that really ruined things for Constantinople. The fourth crusade found itself in the city during a time of great unrest and regime change and decided to take advantage of that instability and ransack the town. They began their siege in the spring of 1204, determined to take the city in the name of their version of Christendom.