Minas Tirith is the capital city of Gondor. Originally known as Minas Anor (the "Tower of the Sun"), it was in built in 3320 S.A. by Anárion, brother of Isildur and second son of Elendil, High King of Arnor. It also known as the White City and City of the Kings. Ostoher rebuilt the city in 420 T.A., and it gradually became more important than Osgiliath, the original capital. King Tarondor finally moved the King's House from Osgiliath to the City in 1640. In the year 2002, Minas Ithil (the "Tower of the Moon") was captured by the Ringwraiths and renamed Minas Morgul. Minas Anor was renamed Minas Tirith, meaning "Tower of Guard", to indicate that since the fall of Minas Ithil, Minas Tirith was to guard Gondor against evil from Mordor. The Rohirrim sometimes translate this into their own language as Mundburg.
Minas Tirith is surrounded by the Rammas Echor, a large ringwall encircling the Pelennor Fields. This wall was built by Ecthelion II but proved no match for the Orc legions of Mordor. The city itself lies on a hill beneath Mount Mindolluin. The city is divided into seven one-hundred-foot high levels, each surrounded by white walls. The gates connecting the levels do not lay behind one another in a line, but face in different directions. A spur of rock, whose summit is level with the city's uppermost tier, juts out from the front of the city in an easterly direction, dividing all but the first level into two. Finally, within the seventh wall, is the Citadel with its White Tower, where the surviving Seeing Stones of Anor kept - three hundred feet high, so that its apex is one thousand feet above the plain gleaming when the light shone on it. Upon the saddle between the city and Mindolluin are the Houses of the Dead - tombs of the Kings of Gondor and their Stewards.
The walls of the city are defended by a battery of 100 trebuchets. These played a significant role in the siege shown in the movie, as they were responsible for destroying many orcs, siege towers and catapults. Sadly, a number of them were smashed to bits by fell beasts, but all were repaired in the end.
Tolkien's description of the physical layout of Minas Tirith is followed scrupulously in Peter Jackson's The Return of the King film, although there is no reason to suppose that the top of the rock is flattened and paved, and in the book it is not the location for the coronation of Aragorn which occurs on the Pelennor Field outside Minas Tirith, he then enters the city as King. In the film version it is within clear sight of the mountains surrounding Mordor and the fires of Mount Doom, so much that in at least one night scene the light of it shines on the faces of viewers from the city walls. However, in the books the mountains were far enough away that from the city they looked like a low dark shadow over the land far away. As well, in the book the populace was almost entirely evacuated before the battle. In the movie, the women and children remained, and many were slaughtered in the lower levels.
During the War of the Ring (Third Age 3018-3019), Minas Tirith is said to "have less than half of the population which could have dwelt at ease" in it.
In The Return of the King, Minas Tirith is besieged by troops of Mordor, the Easterlings and the Haradrim, under the Great Darkness generated by Mordor. The Battle of the Pelennor Fields takes place on March 15 3019 T. A. in the fields surrounding the city. Despite heavy losses, the battle is finally won by Gondor.
On May 1 3019 T.A. King Elessar's coronation took place on the plain outside Minas Tirith, he then entered the city as King.
Minas Tirith is known to stand firm well into the Fourth Age.
The eagle who brings the news of Sauron's defeat to Minas Tirith refers to the city as the Tower of Anor. Although this is nowhere described, it is possible that the city may have reverted to its original name once it no longer needed to guard against evil. An argument against this is that in the abandoned sequel The New Shadow, which takes place during the time of Elessar's son Eldarion, the city was clearly named Minas Tirith.
Map #40 in Barbara Strachey's Journeys of Frodo is a plan of Minas Tirith. Pages 138&139 in Karen Wynn Fonstad's revised The Atlas of Middle-earth is another plan of Minas Tirith. They are at variance with each other, as the only authoritative maps by Tolkien are just sketches.
Note on pronunciation: The i's are long in all cases, thus MEE-nas TEE-reeth.