Short answers, pulled from the story.
Saint Petersburg was founded by Tsar Peter the Great on the 27th of May 1703 on the site of a captured Swedish fortress. Peter laid the foundations of the Peter and Paul Fortress on Zayachy Island, and named the city after the apostle Saint Peter.
The city has been renamed several times. It was originally called Nyenschantz as a Swedish fortress, then Saint Petersburg from 1703. On the 1st of September 1914 Tsar Nicholas II renamed it Petrograd. On the 26th of January 1924 it became Leningrad. A citywide referendum on the 12th of June 1991, in which 55% voted for the original name, restored Saint Petersburg, effective the 6th of September 1991.
The Siege of Leningrad lasted 872 days, from the 8th of September 1941 to the 27th of January 1944. More than one million civilians died, mainly from starvation, and the city's population fell from three million to fewer than 600,000 by the end of 1943.
The Leningrad Symphony is the Seventh Symphony by Dmitri Shostakovich, who was born and raised in Saint Petersburg. He wrote it while based in the city during the siege and dedicated it to Leningrad. It premiered in Samara in March 1942, and received its first performance in the besieged city at the Bolshoy Philharmonic Hall under conductor Karl Eliasberg.
The Lakhta Center is a 462.5 m skyscraper completed in 2019, currently the tallest building in Russia and Europe. It replaced an earlier proposal, the 396 m Okhta Center, which was cancelled in 2010 after the World Monuments Fund listed the Saint Petersburg historic skyline among the 100 most endangered sites. The Lakhta Center's remote location from the historic centre reduced the controversy compared to the original plan.
The Saint Petersburg Conservatory, founded in 1862, trained Pyotr Ilyich Tchaikovsky, Sergei Prokofiev, and Alexander Borodin. Nikolai Rimsky-Korsakov taught there from 1871 to 1905, with Igor Stravinsky among his students. Dmitri Shostakovich was born and raised in the city and taught at the conservatory in the 1960s. Mikhail Baryshnikov, Rudolf Nureyev, and Natalia Makarova trained at the Vaganova Academy of Russian Ballet.