The central focus of the various parades are floats called pasos that have statues of Jesus and Mary. They are brought out of the churches with which the different confraternities are associated and paraded through the streets to very martial music played by marching bands.
I would love to have been a fly on the wall for the conversation that ended with somebody saying, "Sure, let's put an entire tree on it this year."
Because these things are not light and they are carried along the parade routes by burly men called costaleros. People applaud when they re-hoist the float after the various stops to let people kiss the float and take photos. And you can very clearly see the marks on their necks and shoulders afterwards.
(In the linked article I was really struck by the fundamental presumption of Catholicism encoded in this excerpt: "Historically, the Holy Week celebrations also acted as a social leveler, putting on a par the different professional guilds linked to the religious brotherhoods and even African slaves, who were allowed to form their own Seville brotherhood, called 'Los Negritos.' The processions, therefore, 'transcend religion,' Mr. Ruíz González, the historian, argued. 'They gave even excluded people like the slaves a chance to regain some sense of identity.'")
One of the most important pasos is the Virgin of Macarena, who is one of the patron saints of Seville. Toward the end of this video clip, you can see women on the balconies offering prayers and benedictions dedicated to her.
On Easter Sunday, the pasos are returned to the local neighborhood churches, and people pray to them in between the masses and even kiss the bases or the hands of the statues.
I'm really curious about the source of the pseudo-Hebrew on the crucifix: