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

Context paragraphs:
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.

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.

Hugo Award: The Hugo Awards are a set of literary awards given annually for the best science fiction or fantasy works and achievements of the previous year.  The awards are named after Hugo Gernsback, the founder of the pioneering science fiction magazine "Amazing Stories", and were officially named the Science Fiction Achievement Awards until 1992.  Organized and overseen by the World Science Fiction Society, the awards are given each year at the annual World Science Fiction Convention as the central focus of the event.  They were first given in 1953, at the 11th World Science Fiction Convention, and have been awarded every year since 1955.  Over the years that the award has been given, the categories presented have changed; currently Hugo Awards are given in more than a dozen categories, and include both written and dramatic works of various types.

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.

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.

55th World Science Fiction Convention: The 55th World Science Fiction Convention (Worldcon), was LoneStarCon 2, also known as "The Second Occasional LoneStarCon Science Fiction Convention & Chili Cook-off".  The convention was held August 28–September 1, 1997, at the Marriott Rivercenter, Marriott Riverwalk, and the Henry B. Gonzalez Convention Center in San Antonio, Texas, United States.  The first LoneStarCon, held in Austin, Texas, had been the North American Science Fiction Convention (NASFiC) in 1985, when the 43rd Worldcon was held in Australia.

Wiscon: WisCon or Wiscon, a Wisconsin science fiction convention, is the oldest, and often called the world's leading, feminist science fiction convention and conference.  It was first held in Madison, Wisconsin in February 1977, after a group of fans attending the 1976 34th World Science Fiction Convention in Kansas City were inspired to organize a convention like WorldCon but with feminism as the dominant theme.  The convention is now held annually in May, during the four-day weekend of Memorial Day.  Sponsored by the Society for the Furtherance and Study of Fantasy and Science Fiction or "(SF)³", WisCon gathers together women, men, and people of other genders: fans, writers, editors, publishers, scholars, and artists from around the world to discuss science fiction and fantasy, with emphasis on issues of feminism, gender, race, and class.  Writers' workshops are held on the Friday morning of the convention.

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.

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.

71st World Science Fiction Convention: The 71st World Science Fiction Convention (Worldcon), also known as LoneStarCon 3, was held in San Antonio, Texas, on August 29-September 2, 2013, at the Henry B. Gonzalez Convention Center and Marriott Rivercenter.  The convention committee was chaired by Randall Shepherd.  The convention was organized by Alamo Literary Arts Maintenance Organization, Inc. (ALAMO) which had previously organized LoneStarCon 2, the 55th World Science Fiction Convention, held in San Antonio in 1997.

Supporting paragraphs: 68th World Science Fiction Convention Melbourne Convention and Exhibition Centre
Answer: Yarra River