Question: Which piece of work listed did Michelangelo create a wooden model for, but it was never finished?
About the article "Michelangelo", section "Architecture".

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Some have hypothesized that Michelangelo depicted himself in the flayed skin of St. Bartholomew (see below) based on feelings of contempt Michelangelo may have had for being commissioned to paint "The Last Judgment."
Michelangelo often drew himself in a way where he had lost all his power and might.
He questioned over thoughts of dying and the Day of Judgement, which is seen as a reference to this work.
Michelangelo was in his late sixties when he finished this painting, and it has been argued that the peeling of Bartholomew signifies the peeling of the flesh awaiting a new rebirth.
The bearded figure of St. Bartholomew holding the skin was theorized to depict the satirist and erotic writer Pietro Aretino, who had tried to extort a valuable drawing from Michelangelo; this theory has been conclusively refuted because the conflict between Michelangelo and zed Aretino did not occur until 1545, seven years after the fresco's completion. 
To be able to reach the ceiling, Michelangelo needed a support; the first idea was by Julius' favoured architect Donato Bramante, who wanted to build for him a scaffold to be suspended in the air with ropes.
However, Bramante did not successfully complete the task, and the structure he built was flawed.
He had perforated the vault in order to lower strings to secure the scaffold.
Michelangelo laughed when he saw the structure, and believed it would leave holes in the ceiling once the work was ended.
He asked Bramante what was to happen when the painter reached the perforations, but the architect had no answer.
The matter was taken before the Pope, who ordered Michelangelo to build a scaffold of his own.
Michelangelo created a flat wooden platform on brackets built out from holes in the wall, high up near the top of the windows.
Contrary to popular belief, he did not lie on this scaffolding while he painted, but painted from a standing position.
Michelangelo used bright colours, easily visible from the floor.
On the lowest part of the ceiling he painted the ancestors of Christ.
Above this he alternated male and female prophets, with Jonah over the altar.
On the highest section, Michelangelo painted nine stories from the Book of Genesis.
He was originally commissioned to paint only 12 figures, the Apostles.
He turned down the commission because he saw himself as a sculptor, not a painter.
The Pope offered to allow Michelangelo to paint biblical scenes of his own choice as a compromise.
After the work was finished, there were more than 300.
His figures showed the creation, Adam and Eve in the Garden of Eden, and the Great Flood.
The painted area is about 40 m (131 ft) long by 13 m (43 ft) wide.
This means that Michelangelo painted well over of frescoes. 
Lorenzo de' Medici's death on 8 April 1492 brought a reversal of Michelangelo's circumstances.
Michelangelo left the security of the Medici court and returned to his father's house.
In the following months he carved a polychrome wooden "Crucifix" (1493), as a gift to the prior of the Florentine church of Santo Spirito, which had permitted him some studies of anatomy on the corpses of the church's hospital.
Between 1493 and 1494 he bought a block of marble, and carved a larger than life statue of Hercules, which was sent to France and subsequently disappeared sometime circa 18th century.
On 20 January 1494, after heavy snowfalls, Lorenzo's heir, Piero de Medici, commissioned a snow statue, and Michelangelo again entered the court of the Medici.
In the same year, the Medici were expelled from Florence as the result of the rise of Savonarola.
Michelangelo left the city before the end of the political upheaval, moving to Venice and then to Bologna.
In Bologna, he was commissioned to carve several of the last small figures for the completion of the Shrine of St. Dominic, in the church dedicated to that saint.
At this time Michelangelo studied the robust reliefs carved by Jacopo della Quercia around main portal of the Basilica of St Petronius, including the panel of "The Creation of Eve" the composition of which was to reappear on the Sistine Chapel ceiling.
Towards the end of 1494, the political situation in Florence was calmer.
The city, previously under threat from the French, was no longer in danger as Charles VIII had suffered defeats.
Michelangelo returned to Florence but received no commissions from the new city government under Savonarola.
He returned to the employment of the Medici.
During the half year he spent in Florence, he worked on two small statues, a child "St. John the Baptist" and a sleeping "Cupid".
According to Condivi, Lorenzo di Pierfrancesco de' Medici, for whom Michelangelo had sculpted "St. John the Baptist", asked that Michelangelo "fix it so that it looked as if it had been buried" so he could "send it to Rome...pass off as an ancient work and … sell it much better."
Both Lorenzo and Michelangelo were unwittingly cheated out of the real value of the piece by a middleman.
Cardinal Raffaele Riario, to whom Lorenzo had sold it, discovered that it was a fraud, but was so impressed by the quality of the sculpture that he invited the artist to Rome.
This apparent success in selling his sculpture abroad as well as the conservative Florentine situation may have encouraged Michelangelo to accept the prelate's invitation.
Michelangelo arrived in Rome 25 June 1496 at the age of 21.
On 4 July of the same year, he began work on a commission for Cardinal Raffaele Riario, an over-life-size statue of the Roman wine god "Bacchus".
Upon completion, the work was rejected by the cardinal, and subsequently entered the collection of the banker Jacopo Galli, for his garden.
In November 1497, the French ambassador to the Holy See, Cardinal Jean de Bilhères-Lagraulas, commissioned him to carve a "Pietà", a sculpture showing the Virgin Mary grieving over the body of Jesus.
The subject, which is not part of the Biblical narrative of the Crucifixion, was common in religious sculpture of Medieval Northern Europe and would have been very familiar to the Cardinal.
The contract was agreed upon in August of the following year.
Michelangelo was 24 at the time of its completion.
It was soon to be regarded as one of the world's great masterpieces of sculpture, "a revelation of all the potentialities and force of the art of sculpture".
Contemporary opinion was summarized by Vasari: "It is certainly a miracle that a formless block of stone could ever have been reduced to a perfection that nature is scarcely able to create in the flesh."
It is now located in St Peter's Basilica. 
The Medici Pope Leo X gave Michelangelo the commission to design a façade in white Carrara marble in 1518.
Michelangelo made a wooden model, which shows how he adjusted the classical proportions of the facade, drawn to scale, after the ideal proportions of the human body, to the greater height of the nave.
The work remained unbuilt.
Michelangelo did, however, design and build the internal facade, seen from the nave looking back toward the entrances.
It comprises three doors between two pilasters with garlands of oak and laurel and a balcony on two Corinthian columns.
In recent years, the association of “Friends of the Elettrice Palatina” and the Comune of Florence re-visited the question of completing the outer facade according to Michelangelo's designs.
To assist with the public debate, a computerized reconstruction was projected onto the plain brick facade in February 2007.
As yet, no decision has been made on the project.
The campanile dates from 1740. 
Michelangelo, at 17, was working under the patronage of Lorenzo de' Medici when he crafted the "Battle of the Centaurs", although the work was not commissioned but created for himself.
The work reflected a then current fashion for reproducing ancient themes.
Specifically, Michelangelo was inspired by a relief that had been produced for de' Medici by Bertoldo di Giovanni, a work in bronze that hung in the Medici palace.
Michelangelo chose to work in marble rather than the more expensive bronze to keep down costs.
Bertoldo's work, The "Equestrian Battle in the Ancient Manner"—also known as "Battle (with Hercules)"—was a recreation of a damaged Roman battle sarcophagus and required liberal imagination to fill in the gaps left by the damaged original.
Bertoldo took other liberties with his source material and seems to have himself been inspired by the Antonio del Pollaiolo engraving "Battle of the Nudes".
The young sculptor never finished the work.
While a number of biographies have attributed this to the loss of power of the Medici family, contemporary Michelangelo biographer Eric Scigliano argues that Michelangelo had plenty of time to finish the sculpture if he had chosen to and points out that this was only the first of several "non finito" sculptures, preceding the "Taddei Tondo" and "Pitti Tondo".
He also notes that Michelangelo expressed no dissatisfaction with the work.
Whether or not the sculpture was intentionally left incomplete, Michelangelo regarded this sculpture as the best of his early works.
He kept it, though he destroyed or abandoned many of his other pieces, and remarked to his biographer Ascanio Condivi later in his life that looking at it made him regret the time he'd spent in pursuits other than sculpture.