The Vatican City State, referred to as the Vatican, the capital of Vatican City, is the smallest country in the world with a land area of 0It is 44 square kilometers and is located on the high ground in the northwest corner of the city of Rome, Italy.
It belongs to the ** Mediterranean climate, with an average annual temperature of 16, an average temperature of 7 in January and an average temperature of 24 in July. As of January 2023, it has a permanent population of 618 people, mainly Italians. 
The Vatican has its own banks, post offices, telecommunications and other public service institutions, but its natural resources are scarce, there is no industrial and agricultural production, and its financial revenue mainly depends on tourism, the issuance of stamps and coins, the rental of real estate, the profits of religious banks, and donations from believers.
In 756 AD, Pope Stephen II received a gift from King Pepin of the Franks to the city of Rome and the surrounding area, with religious and secular administration. After that, the Papal States were established in central Italy.
It was annexed by the Kingdom of Italy in 1870.
In February 1929, Mussolini signed the Lateran Treaty with Pope Pius XI, in which the Pope officially recognized the destruction of the Papal States and established the Vatican City State, and Italy recognized the Vatican as a sovereign state, and sovereignty belonged to the Pope.
The Vatican is a theocratic state – the Pope is the head of the Vatican and has the highest legislative, executive, and judicial powers. 
The Pope calls himself "the successor of the Apostle Peter" and is the spiritual leader of Catholics in all countries of the world.
The Vatican has universities or seminaries in Italy, France, Spain, Belgium, the United States, Canada, Brazil, Chile, Ethiopia, the Philippines, Japan, and many countries and regions around the world.
The Vatican Museums are one of the most famous museums in the world, with countless art collections and more than 5 million visitors a year. 
As of January 2023, the Vatican has established diplomatic relations with 183 countries, regions and organizations. The Vatican is a member of the OECD and an observer to important international or regional organizations such as the United Nations, the OSCE, the Food and Agriculture Organization of the United Nations, the Universal Postal Union, and the World Intellectual Property Organization. The Vatican and China do not currently have diplomatic relations.
The Vatican's defense forces are divided into the Swiss Guards and the Vatican Gendarmerie.
The Swiss Guard, numbering about 110 people, was responsible for protecting the Pope, dignitaries and all buildings belonging to the Pope.
The Vatican Gendarmerie numbered about 130 and was responsible for social order, border control, traffic control, criminal investigations and general policing in Vatican City.
The most important buildings in the Vatican City State are St. Peter's Basilica and St. Peter's Square – the most outstanding Renaissance building, St. Peter's Basilica is the largest church in the world with a total area of 230,000 square meters, the main building is 454 meters, about 211 meters long, can accommodate up to nearly 60,000 people to pray at the same time.
In addition to the church, Castel Sant'Angelo, located on the Tiber River, is also part of the Vatican's territory. The earliest castle was the burial place of the Roman Emperor Hadrian for his family.
It is said that in 509 A.D., when the Roman epidemic was rampant, the pope at that time passed by after Mass, and suddenly an angel with a sword appeared, and since then the epidemic has disappeared, so the castle was renamed Castel Sant'Angelo. The castle and the church were connected by walls, so that the Pope did not have to pass through Italian soil to get from St. Peter's Basilica to Castel Angel.
Ponte Sant'Angelo Bridge'Angelo, also known as Pons Aelius, is an ancient Roman bridge over the Tiber River, built by the Roman Emperor Hadrian in 134 AD to connect the city center with his newly built mausoleum, now Castel Sant'Angelo.
The Bridge of Sant'Angelo is the most beautiful bridge in Rome, with statues of twelve angels, each holding an instrument of Jesus' torture, all of which were made by Bernini.
It is said that we walked all the way from the ancient city of Rome, standing on the bridge over the Tiber River, and saw the legendary great dome and the beautiful Sant'Angelo Bridge from afar, but unfortunately we didn't have time to walk the beautiful Sant'Angelo Bridge.
The guide took us across the street through normal security and into the world's smallest country – walking from the streets of Rome to another country felt like going to the street to buy groceries and go home, haha.
The first thing you see when you enter the door is the large pillars, which are quite like the Great Pillar Hall of the Luxor Temple in Egypt (the largest open-air museum on earth - Luxor).
But it is elegant in the ancient Greek style.
Passing through the Pillared Hall, you will see a wide circular square. The square stands the towering Egyptian obelisk.
and two beautiful fountains on either side of the obelisk.
Numerous sculptures of human figures stand on the roofs of the buildings on both sides of the circular square, which look spectacular against the evening sky.
The domed building surrounded by two semi-circular buildings is the great St. Peter's Basilica.
More exciting and listen to the next breakdown.
The popular science knowledge and part of this article are from the encyclopedia and the documentaries "Treasures of Ancient Greece" and "Deciphering Ancient Rome".