Short answers, pulled from the story.
Rijeka sits on the narrow strip of land where the Dinaric Alps meet the Adriatic Sea at the mouth of the river Rječina. The city lies roughly equidistant from Milan, Budapest, Munich, Vienna, and Belgrade while being bordered by mountains on three sides.
Pliny the Elder first mentioned Rijeka as Tarsatica in his Natural History in the 1st century AD. Around AD 150, the Greek geographer Ptolemy described it again when writing about Illyria or Liburnia.
Emperor Charles VI declared the Port of Rijeka a free port together with the Port of Trieste in 1719. He had the trade route to Vienna expanded in 1725 to facilitate commerce.
In 799, Rijeka was attacked by Frankish troops under Charlemagne during the Siege of Trsat which resulted in the death of Duke Eric of Friuli. The Frankish forces finally occupied and devastated the castle after initially repulsing the attack.
On the 14th of July 1942, Italian military killed 100 men from suburban village Podhum and resettled the remaining 800 people to concentration camps. This event is known as the Podhum massacre and occurred during World War II.