Question: What river is the location of the 68th World Science Fiction Convention next to?

full_context: Document 1: Federation Square: Federation Square is a mixed-use development in the inner city of Melbourne, covering an area of and centred on three major public spaces – St. Paul's Court, The Square, and The Atrium. Built on a concrete deck above busy railway lines, it is located at the intersection of Flinders Street and Swanston Street/St Kilda Road in the city's Central Business District, adjacent to Flinders Street railway station.
Document 2: Oz Comic Con: Oz Comic Con is a speculative fiction entertainment and comic convention that has been running since 2012 within various major Australian cities, and is a local franchise of the New York Comic-Con. Attendees have included Nintendo Australia. Oz Comic Con currently runs in the cities of Perth, Adelaide, Melbourne, Brisbane and Sydney.
Document 3: 10th World Science Fiction Convention: The 10th World Science Fiction Convention was held on Labor Day weekend from August 30 to September 1, 1952, at the Morrison Hotel in Chicago, Illinois. This Worldcon never chose an official name other than the title "10th World Science Fiction Convention," as both the convention's issued membership card and program book clearly stated. Only the first Worldcon in New York City (1939) and the 11th in Philadelphia, 1953, shared this lack of a formal convention name. The phrases "Tenth Anniversary World Science Fiction Convention" (TAWSFiC) and "Tenth Anniversary Science Fiction Convention" (TASFiC, likely a simple linotype error, as "World" is missing) were each used in some of this Worldcon's pre-convention materials; the phrase's acronyms "TAWSFiC" and "TASFiC" were never officially used in print or otherwise by the Chicago committee at that time. However, the 10th Worldcon "was" frequently referred to by its members by the unofficial name Chicon II, so dubbed after the previous Chicago Worldcon (Chicon) in 1940; this name proved so popular that the convention became known as Chicon II in science fiction fandom's lore and written histories.
Document 4: Southbank, Victoria: Southbank is an inner urban neighbourhood of Melbourne, Victoria, Australia, 1 km south of Melbourne's central business district. Its local government area are the Cities of Melbourne and Port Phillip. At the 2011 Census, Southbank had a population of 11,235. Its northernmost area is considered part of the Central Business District and Central Activities District of the City. Southbank is bordered to the north by the Yarra River, and to the east by St Kilda Road. Southbank's southern and western borders are bounded by Dorcas Street, Kings Way, the West Gate Freeway and Montague Street.
Document 5: South Yarra, Victoria: South Yarra is an inner suburb of Melbourne, Victoria, Australia, 4 km south-east of Melbourne's Central Business District, located within the Cities of Melbourne and Stonnington local government areas. South Yarra recorded a population of 25,147 at the 2016 Census.
Document 6: 75th World Science Fiction Convention: The 75th World Science Fiction Convention (Worldcon), also known as Worldcon 75, was held 9–13 August 2017 at the Helsinki Exhibition and Convention Centre in Helsinki, Finland. This location was selected in August 2015 by the members of the 73rd World Science Fiction Convention in Spokane, Washington.
Document 7: 68th World Science Fiction Convention: The 68th World Science Fiction Convention (Worldcon), Aussiecon Four, was held 2–6 September 2010, in the Melbourne Convention and Exhibition Centre in Melbourne, Victoria, Australia, the location selected by the members of Denvention 3.
Document 8: Melbourne Convention and Exhibition Centre: The Melbourne Convention and Exhibition Centre is the name given to two adjacent buildings next to the Yarra River in South Wharf, an inner-city suburb of Melbourne, Victoria, Australia. The venues are owned and operated by the Melbourne Convention and Exhibition Trust.
Document 9: Southbank, Victoria: Southbank is an inner urban neighbourhood of Melbourne, Victoria, Australia, 1 km south of Melbourne's central business district. Its local government area are the Cities of Melbourne and Port Phillip. At the 2011 Census, Southbank had a population of 11,235. Its northernmost area is considered part of the Central Business District and Central Activities District of the City. Southbank is bordered to the north by the Yarra River, and to the east by St Kilda Road. Southbank's southern and western borders are bounded by Dorcas Street, Kings Way, the West Gate Freeway and Montague Street.
Document 10: 74th World Science Fiction Convention: The 74th World Science Fiction Convention (Worldcon), also known as MidAmeriCon II, was held August 17–21, 2016, at the Bartle Hall Convention Center in downtown, Kansas City, Missouri. Its location was selected on August 17, 2014 by the members of the 72nd World Science Fiction Convention in London.
Document 11: 48th World Science Fiction Convention: The 48th World Science Fiction Convention (Worldcon), was ConFiction, which was held in The Hague, Netherlands 23rd-27 August 1990 at the Netherlands Congress Centre. This convention was one of the two Worldcons held in continental Europe, the other being the 28th World Science Fiction Convention held in West Germany.
Document 12: 16th World Science Fiction Convention: The 16th World Science Fiction Convention, also known as Solacon, was held August 29–September 1, 1958, at the Alexandria Hotel in Los Angeles, California, United States. Solacon was physically in Los Angeles, but (by mayoral proclamation) technically in South Gate, California, to fulfill their bid slogan of "South Gate in '58."
Document 13: Arts Centre Melbourne: The Arts Centre Melbourne, originally known as the Victorian Arts Centre and briefly officially called the Arts Centre, is a performing arts centre consisting of a complex of theatres and concert halls in the Melbourne Arts Precinct, located in the central Melbourne suburb of Southbank in Victoria, Australia.
Document 14: Melbourne Sports and Entertainment Precinct: The Melbourne Sports and Entertainment Precinct is a series of sports stadiums and venues, located in Melbourne, Victoria, in Australia. The precinct is situated around 3 km east of the Melbourne city centre, located in suburbs of Melbourne and Jolimont, near East Melbourne and Richmond.
Document 15: Docklands, Victoria: Docklands (also known as Melbourne Docklands to differentiate it from London Docklands) is an inner-western suburb of Melbourne, Victoria, Australia, 2 km (1.2 mi) from Melbourne's Central Business District. Its local government area is the City of Melbourne. At the 2016 Census, Docklands had a population of 10,964.
ground_truth: Yarra River