Question: What structure did Michelangelo create a wooden moden for, but never complete?
About the article "Michelangelo", section "Architecture".

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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. 
Michelangelo's architectural commissions included a number that were not realised, notably the facade for Brunelleschi's Church of San Lorenzo in Florence, for which Michelangelo had a wooden model constructed, but which remains to this day unfinished rough brick.
At the same church, Giulio de' Medici (later Pope Clement VII) commissioned him to design the Medici Chapel and the tombs of Giuliano and Lorenzo Medici.
Pope Clement also commissioned the Laurentian Library, for which Michelangelo also designed the extraordinary vestibule with columns recessed into niches, and a staircase that appears to spill out of the library like a flow of lava, according to Pevsner, "...revealing Mannerism in its most sublime architectural form.
"In 1546 Michelangelo produced the highly complex ovoid design for the pavement of the Campidoglio and began designing an upper storey for the Farnese Palace.
In 1547 he took on the job of completing St Peter's Basilica, begun to a design by Bramante, and with several intermediate designs by several architects.
Michelangelo returned to Bramante's design, retaining the basic form and concepts by simplifying and strengthening the design to create a more dynamic and unified whole.
Although the late 16th-century engraving depicts the dome as having a hemispherical profile, the dome of Michelangelo's model is somewhat ovoid and the final product, as completed by Giacomo della Porta is more so.
Mozart received a commission for three quartets in 1785 from the publisher Franz Anton Hoffmeister.
Hoffmeister thought this quartet was too difficult and that the public would not buy it, so he released Mozart from the obligation of completing the set.
(Nine months later, Mozart composed a second quartet anyway, in E-flat major, K. 493).
Hofmeister's fear that the work was too difficult for amateurs was borne out by an article in the "Journal des Luxus und der Moden" published in Weimar in June 1788.
The article highly praised Mozart and his work, but expressed dismay over attempts by amateurs to perform it: "performed by amateurs it "could" not please: everybody yawned with boredom over the incomprehensible "tintamarre" of 4 instruments which did not keep together for four bars on end, and whose senseless "concentus" never allowed any unity of feeling; but it "had to" please, it "had" to be praised!
... what a difference when this much-advertised work of art is performed with the highest degree of accuracy by four skilled musicians who have studied it carefully."
The assessment accords with a view widely held of Mozart in his own lifetime, that of a greatly talented composer who wrote very difficult music.
At the time the piece was written, the harpsichord was still widely used.
Although the piece was originally published with the title "Quatuor pour le Clavecin ou Forte Piano, Violon, Tallie et Basse," stylistic evidence suggests Mozart intended the piano part for "the 'Viennese' fortepiano of the period" and that our modern piano is "a perfectly acceptable alternative."
In 1504 Michelangelo Buonarroti was commissioned by Pier Soderini to complete a celebrative fresco depicting the Battle of Cascina, to be placed in the Florentine Room of the Great Council (or Salone dei Cinquecento) of Palazzo Vecchio while Leonardo da Vinci was commissioned to complete another painting on the opposite wall to celebrate the equally important Florentine victory at the 1440 Battle of Anghiari.
Neither picture now exists.
Michelangelo never executed his, and Leonardo's was irretrievably ruined soon after being completed because of the innovative, but disastrous, painting method adopted by the artist.
However, a number of studies for Michelangelo's work do exist, and he completed a full-size cartoon of the intended composition.
Michelangelo prepared his cartoon in a hospital room of the "Sant'Onofrio Dyers" after payment of a monthly salary.
The subject is the beginning of the battle, when the overheated Florentine soldiers, having divested themselves of their armor, are swimming in the Arno river.
The soldiers are depicted leaping from the river and buckling on their armor on hearing the trumpet warning them of the imminent Pisan attack.
This subject allowed Michelangelo to depict a group of naked bodies in contrapposto.
Though the original cartoon is lost, having allegedly been cut up by Michelangelo's rival Baccio Bandinelli, a number of copies exist, along with an engraving by Marcantonio Raimondi. 
The following is a list of works of painting, sculpture and architecture by the Italian Renaissance artist Michelangelo.
Lost works are included, but not commissions that Michelangelo never made.
Michelangelo also left many drawings, sketches, and some works in poetry.