Short answers, pulled from the story.
Construction of St. Peter's Basilica began on the 18th of April 1506 and was completed in 1615, with Pope Urban VIII solemnly dedicating it on the 18th of November 1626. The project spanned more than 120 years and involved over twenty popes and a succession of architects including Bramante, Raphael, Michelangelo, Maderno, and Bernini.
St. Peter's Basilica is the largest Christian church building in the world by interior area, with an interior of 15,160 square metres and an exterior area of 21,095 square metres. It is also home to the tallest dome in the world, which rises 136.57 metres from the basilica floor to the top of the external cross.
St. Peter's contains over 100 tombs, including those of 91 popes. Notable non-papal burials include Queen Christina of Sweden, Countess Matilda of Tuscany, Holy Roman Emperor Otto II, composer Giovanni Pierluigi da Palestrina, and members of the exiled House of Stuart. The most recent interment was Pope Benedict XVI, on the 5th of January 2023.
The dome was principally conceived by Michelangelo, who redesigned it in 1547 as an ovoid structure with two brick shells and sixteen outer stone ribs. He died in 1564 with only the drum complete. Giacomo della Porta, working with Domenico Fontana under Pope Sixtus V, brought the dome to completion in 1590.
The baldacchino is a bronze canopy 28.74 metres tall designed by Gian Lorenzo Bernini, which stands beneath the dome and directly above the papal altar. Its four twisted columns were modelled on ancient columns from Constantine's original basilica, themselves said to reference the columns of the Temple of Jerusalem. It is claimed to be the largest freestanding bronze object in the world.
To help finance construction, Albrecht, Archbishop of Mainz and Magdeburg, promoted the sale of indulgences and appointed the Dominican preacher Johann Tetzel to carry out the campaign. Tetzel's aggressive salesmanship provoked a scandal that became one of the direct triggers of the Protestant Reformation.