Short answers, pulled from the story.
The UNESCO World Heritage Site in Seville comprises three buildings within the old town: the Alcázar palace complex, the Cathedral, and the General Archive of the Indies. These three monuments are contained in an old town area of approximately four square kilometres.
Seville was chosen in 1503 because it was the largest demographic, economic, and financial centre of Christian Andalusia in the late Middle Ages. Additional factors included the Andalusian coastline being largely controlled by the House of Medina Sidonia, the city's important hinterland and administrative expertise, and its inland location providing military security and easier tax enforcement.
Seville's monopoly began to break down in the early 17th century as silting of the Guadalquivir in the 1620s made the river harder to navigate. The fleets of the Indies transferred to Cádiz in 1680, and the Casa de Contratación itself relocated there in 1717.
The 1391 pogrom in Seville killed around 4,000 Jews and forced many others to convert to Christianity. All of Seville's synagogues were seized and converted into churches, and the land and shops of the Jewish quarter were appropriated by the church.
A 2012 study by experts concluded that 153 operas have been set in Seville, more than in any other city in Europe. Among them are works by Beethoven, Mozart, Rossini, Donizetti, and Bizet.
Seville has a hot-summer Mediterranean climate and is the warmest city in continental Europe, with an annual average temperature of 19.6 degrees Celsius and summer average daily highs above 36 degrees. The hottest temperature ever recorded at Seville Airport was 46.6 degrees Celsius on the 23rd of July 1995. Seville was also the first city in the world to formally name a heat wave, calling it "Zoe".