Short answers, pulled from the story.
Rijeka means "river" in Croatian, and Fiume is the Italian word for the same. All historical names for the city, including the Latin Flumen and the Slovene Reka, carry the same meaning, reflecting the city's location at the mouth of the river Rjecina. Today, the name Fiume has no official status for legal reasons, though Rijeka's Italian community has sought to restore bilingual signage at city entrances.
Rijeka was first recorded in the 1st century AD when Pliny the Elder noted it as Tarsatica in his Natural History (iii.140). Around AD 150, the Greek geographer Ptolemy also mentioned it in his Geography when describing the location of Illyria and Liburnia.
Gabriele D'Annunzio was an Italian poet and nationalist who on the 12th of September 1919 led a force of Italian irregulars to seize Rijeka after peace negotiations over the city collapsed. He established the Italian Regency of Carnaro, an independent state that attracted figures including Arturo Toscanini and Guglielmo Marconi, and was the first state to recognize Soviet Russia. Italian royal forces ended his occupation after five days of resistance in late December 1920, an episode known as Bloody Christmas.
After Yugoslav forces entered Rijeka on the 3rd of May 1945, at least 650 Italians were executed, and the Autonomist leaders who had aided the Partisans were assassinated by the Yugoslav secret police OZNA. In the years leading to the Trieste Crisis of 1954-58,000 of the city's 66,000 inhabitants chose to emigrate. The city was subsequently resettled by immigrants from across Yugoslavia, fundamentally changing its demographic and linguistic character.
The Rijeka Carnival is an annual pre-Lent festival established in 1982, now the largest carnival in Croatia. It has grown from three masked groups in its founding year to around 15,000 participants organized in over 200 carnival groups, drawing crowds exceeding 100,000. The carnival opens when the mayor symbolically hands the city keys to Meštar Toni, the carnival maestro.
Rijeka was home to the world's first self-propelled torpedo, tested by Robert Whitehead and Giovanni Luppis on the city's launch ramp in 1866, with the Whitehead Torpedo Works formally opening in 1874. The city also hosted the first industrial-scale oil refinery in Europe in 1882. In 1886, Austrian physicist Peter Salcher, working at the city's Marine Academy, took the first photograph of a bullet in supersonic flight, a technique later used by Ernst Mach.