The Western Wall (HaKotel HaMa'aravi or in short The Kotel) is a wall that survived from the Jewish second temple mount period, in Jerusalem. 

The wall is a holy place to the Jewish people because it was the closest to the Holy of Holies, which is the most holy place for Jews.

Millions have come to the wall as tourists and pilgrims, over the decades, to be able to touch the stones and feel the sanctity that emanates from it.
The wall is a place for people from all over the world to come to: foreign heads of states visit the wall due to their respect for its meaning to Jews, every tourist that visits Israel visit the wall and almost everyone in Israel visits the wall a least once.
For years and until today the wall continues to have influence on the devotion and belief of Jews all over the world.

The first temple or was built in the 10th century BC, and was destroyed by the Babylonians in 586 BC.
The second temple was destroyed by the Roman Empire in AD 70 as a result of the  first war between the Jewish people and the Romans.
Each Temple stood for about four centuries.
The place is holy to Muslims too. They believe that the prophet Muhammad made a journey to Jerusalem in 620 CE.
He arrived on a winged horse named Al-Buraq, and tethered the horse to a wall, which some Muslims believe to be the Western wall.

In the Jewish belief the holy of holies was in the temple that was the most sacred building to the Jews.
The site has become a traditional place for prayers and wailing by the Jewish people that wail over the suffering they endure through the years they exists, there for it is also named Wailing Wall. 

The Ottoman Empire (Turkey) ruled over the wall for 400 years between 1515 and 1917.
Then the British Mandate of Palestine has took charge over the place between 1917 and 1948 and then the Jordanian ruled Jerusalem between 1948 and 1967.
Over these periods the Jews did not had a free access to the wall.
Only in the Six day war, at 1967,  when the Israel defense forces won a victory, they had free access to the site, when they got control over Jerusalem and the west bank.

Since 1967, it has become a custom among many Jews throughout the world to hold their Bar Mitzvah services at the wall.

The Western Wall Web Site                 Jerusalem Municipal Web Site              Jerusalem