Dome of the Rock ("Qubbat al-Ṣakhrah" in Arabic), whose golden dome has become the iconic symbol of Jerusalem, is an Islamic shrine on the Temple Mount. This shrine isn't a mosque but a large octagonal structure that supports a dome over a rock, hence its name.
Why was the Dome of the Rock built on Temple Mount, the plateau of Jerusalem where the Jewish Temple of Jerusalem once stood?
The official reason is that it was built to commemorate Mohammed flying on a horse named Buraq from Mecca to Al Aqsa Mosque, which is also on the Temple Mount, and from there to heaven for a visit. But horses have trouble flying and Mohammed died decades before Al Aqsa Mosque was built (see Al Aqsa Mosque).
What is the real reason?
After conquering Jerusalem, the ninth Islamic Caliph, Abd al-Malik built the Dome of the Rock to commemorate his conquest of Judaism's capital. That is why it was built on the spot of the Temple Mount where the Jewish Temple of Jerusalem had once stood.
For the next 1,300 years, Dome of the Rock served as a flag of victory for whoever conquered Jerusalem. When the Crusaders captured Jerusalem in 1099, they turned it into a Catholic church. When Saladin recaptured Jerusalem in 1187, he turned it back into a Muslim shrine.
When the Israeli army captured the Temple Mount during the Six Day War in 1967, Arik Achmon and Ezra Orni, two Israeli paratroopers, climbed up the Dome of the Rock and hung the Israeli flag on top of it until Moshe Dayan, the then Israeli Defense Minister, ordered it to be taken down, saying, "Do you want to see the Middle East on fire?"
The Israeli government declared sovereignty over the Temple Mount but "in order to keep peace," handed over its management to a Muslim trust led by the Ministry of Religious Affairs and Trusts of Jordan, Israel's Muslim neighbor to the east. Surprisingly, the orthodox Jews supported this decision.
Why?
Inside the Jewish Temple was the "Holiest of All," the most holy place, the entry into which was forbidden for all but the high priest, and even he could enter only once a year. Because the current assessment of the exact location of the Holiest of All is uncertain, the orthodox Jews feared inadvertently treading on the former site of the Holiest of All. Rabbis in Jerusalem still forbid their flock from setting foot on the Temple Mount for this reason but many Jews remain troubled - even indignant - that a Muslim shrine sits atop the site of their Temple, including the Holiest of All.*
Is the Dome of the Rock's golden dome made of gold?
The "golden" dome was covered with lead until 1963, and then with gold-colored aluminum. Despite Muslims' unanimous expressions of reverence for the Dome of the Rock, their pleas for their leaders to cover its golden dome actually with gold went unheeded until 1993, when the former king of Jordan sold one of his mansions in London and used the proceeds to buy the needed 180 pounds of gold.
The interior of the Dome of the Rock is made of wood and its exterior facade is porcelain, which simply sits on an octagonal marble base.
* The "Holiest of All," also called, "the Most Holy Place," covered 100 square yards (And he made the Most Holy Place. Its length was according to the width of the house, twenty cubits, and its width twenty cubits... (2 Chronicles 3:8); one cubit equals 18 inches, so 20 x 20 cubits equal 10 x 10 yards) and was situated west of the geographic center of the Temple Mount. The octagonal Dome of the Rock is also situated west of the geographic center of the Temple Mount but covers almost 2,000 square yards (20 yards per side of the octagon). This means that the Dome of the Rock, which is about 20 times larger, almost certainly covers the former site of the Temple of Jerusalem's Holiest of All, entering which was a very serious matter even for the high priest, except for the "High Priest" mentioned here and explained here.
Travel Tip
As in any foreign land, the locals appreciate being greeted in their own
language. To greet a Jew, say "Shalom," which means
"Peace." To greet an Arab, say "Salaam Wa Ah-lay-koom," which means "Peace
be with you." The Arab will reply, "Wa Ah-lay-koom salaam,"
meaning "Peace be with you too,"
while the Jew will simply reply,
"Shalom."