The Mysterious Flame of Queen Loana Chapter 10
Revolt of the Wool Carders
In late medieval Florence, the disenfranchised ciompi ("wool carders") were a class of labourers in the textile industry who were not represented by any guild. In 1378 they launched the Revolt of the Ciompi, a briefly successful insurrection of the disenfranchised lower classes. The revolt briefly brought to power in 14th-century Florence an unprecedented level of democracy. They were defeated by the more conservative elements in Florentine society when the major and minor guilds closed ranks to reestablish the old order. from 
Battle of Montaperti
one of those complicated stories from the fog of the middle ages involving Florentines, papal authority, and feuding families.
"would it not be enough to sit here looking at that hill that is so beautiful, as that novel said, what was it called?"
The book being referenced is, once again, Eco's own Foucault's Pendulum, which ends with the lines "So I might as well stay here, wait, and look at the hill. It's so beautiful" (the hill is mentioned several times throughout the book in addition to the ending.) The hill is known as the Bricco (di Brunate,) and is surmounted by the Santa Maria della Grazie chapel. It is located near the town of La Morra in the Langhe region of the Italian Piemonte. Eco references the hill several times in Queen Loana, including references to the Laghe region; it is likely that he is, in fact, speaking of the same hill in both of these novels. (Even the same where Yambo sent his grandchildren picking flowers that, according to Paola, only combined in the minds of mad poets - p. 160 or 161.)
"to raise three pavilions"
Mark 9:5 "Peter said to Jesus, "Rabbi, it is good for us to be here. Let us put up three shelters—one for you, one for Moses and one for Elijah." 
a plot device from Sherlock Holmes novels and probably countless other fictions.
a walled-up doorway
in chapter 64 of Foucault's Pendulum, Belbo describes a dream: "Sometimes I'm in a country house. It's big, I know there's another wing, but I've forgotten how to reach it, as if the passage had been walled up. . In that other wing there are rooms and rooms.... shelves filled with books, a complete set of the Illustrated Journal of Travel and of Adventures on Land and Sea. It's not true that ... Mama gave them to the trash man." Yambo has already been exploring rooms like those in Belbo's dream, and on p. 134 he found the very magazines Belbo longed for.