Vatican City is a small enclave within Rome on the banks of the Tiber River. It has a population of less than a thousand and a size of no more than a couple of acres. The Pope of the Catholic Church has total legislative, executive, and judicial power here, and he serves until his death unless he abdicates his position of his own accord. The College of Cardinals serves as an advisory body to the Pope and elects the next Pope upon his death.
Vatican City is a small survivor of the Papal States that at one point in the mid-19th century comprised of 17,000 square miles. Due to Italian unification at the time, most of this area was consolidated into Italy, with a small area protected. After much bickering, the Lateran Treaty in 1929 led to the modern day version of Vatican City, with decentralized power and more emphasis on the autonomy of the bishops.