Italians did this backwards and it worked perfectly!
Italy is a country that in spirit was alive since Rome was founded by Romulus back in the 8th century before Christ. After that, the Italian peninsula was a melting pot of cultures that due to innumerable circumstances, ended up dividing the territory and its people. September 20t 1870 is the date when Italy unified itself and the last territory was added to the unified country. However, Italians did this backwards. 12 years before the unification, Italy was divided in 8 states. Some of those states were ruled by Italians and some were by foreign powers that benefited from this division.
One might think that this magnificent master plan of unification came from the center of the country. So it would be reasonable to think that Rome was the one that started everything. However, Rome (current capital of Italy) was the last territory conquered by the Bersaglieri on the last day of summer of 1870. The campaign to complete the unification started on May 5th 1860 and it took 10 years to be completed. The Vatican State was the last state standing and it occupied the region currently know as Lazio.
So Rome was the last city added to Italy. Indeed, Italians crowned Rome as capital of the country as soon as the could since that was the original intention and it became a symbol for the incredible victory. We can confidently say that this case is unique because typically is powerful cities that like to be recognized for it's victory over others. In this case, Rome was defeated and then rewarded with the very same role she always desired since the times of it's empire.