Question: How long is the river that divides the neighborhood of Downtown Miami?

Context paragraphs:
Miami Riverwalk: The Miami Riverwalk is a pedestrian walkway located in Downtown Miami, Florida.  It extends along the north side of the Miami River and the Biscayne Bay.  It begins at Bayfront Park and ends one block west of the South West 2nd Street bridge where the path leads back to South West -North River Drive.  The Riverwalk is currently blocked at two points along this route by developers, for one block at the mouth of the river by a temporary sales office for the former Epic Residences & Hotel 2 Tower, and at the west side of the South Miami Avenue bridge by the One River Point Condo tower site at Riverfront.  The Riverwalk passes under the Brickell Avenue Bridge, built in 1915, carrying Brickell Avenue, South Miami Avenue Bridge, Miami Metrorail, South West 2nd Street Bridge, and ends under the I-95 overpass.  Since 2008, the Miami Riverwalk Festival has been held in November, which includes a lot of free and cultural entertainment.  The Riverwalk is a part of a broader project known as the Miami River Greenway which also includes an incomplete greenway along the south side of the river.

Central Business District (Miami): Central Business District (CBD) is the historic city center of what has become Greater Downtown Miami, in Miami, Florida, United States.  It is generally bound by Biscayne Boulevard, Bayfront Park and Museum Park on the east, the Miami River to the south, North 6th Street to the north, and Interstate 95 to the west.  While it is technically Miami's official "downtown", the term "Downtown Miami" has come to refer to a much larger 3.8 sqmi area along the bay from the Rickenbacker Causeway to the Julia Tuttle Causeway.  It is also distinct from the financial district, which in this case is neighboring Brickell to the south.  However, the downtown core has over 5000000 sqft of office space, including more than fifteen buildings with greater than 100000 sqft of floor space.

Miami River Greenway: The Miami River Greenway is an urban greenway project in Miami, Florida located along both banks of the Miami River.  The plan is for it to eventually form an uninterrupted walkway from the mouth of the river in Downtown Miami to the Dolphin Expressway near the Civic Center area, and in the long term all the way to Miami International Airport.  On the north bank the walkway is currently known as the Miami Riverwalk which currently extends beyond the river through Bayfront Park along Biscayne Bay where it is known as the Bay Walk.  Plans are to extend this as far north and south as the Julia Tuttle and Rickenbacker Causeways, respectively.

Greater Downtown Miami: Downtown Miami is an urban city center, based around the Central Business District of Miami, Florida, United States.  In addition to the central business district, the area also consists of the Brickell Financial District, Historic District, Government Center, Omni and Park West.  The neighborhood is divided by the Miami River and is bordered by Midtown (Edgewater and Wynwood) to the north, Biscayne Bay to the east, Civic Center and Overtown to the west, and Coconut Grove to the south.

Flagler Street: Flagler Street is a 12.4 mi main east–west road in Miami.  Flagler Street is the latitudinal baseline that divides all the streets on the Miami-Dade County grid plan as north or south streets.  (The east-west division is along Miami Avenue) Flagler Street is named after industrialist Henry Flagler and serves as a major commercial east–west highway through central Miami-Dade County, with a mixture of residential neighborhoods (featuring apartment complexes) and strip malls, the commercial presence increasing as SR 968 approaches downtown Miami.

Government Center (Miami): Government Center is a district in Downtown Miami, Florida.  Bounded roughly by I-95 and NW 3rd Avenue to the west, SW 1st Street to the south, NW 5th Street to the north, and NE 1st Avenue to the east, Government Center is located on the western edge of downtown.  The area includes several courthouses, including the historic Miami-Dade County Courthouse and a US district court, the City of Miami police headquarters, city, county, and state offices.  The eponymous and most used county transit station, Government Center, serving Metrorail, Metromover, and Metrobus, is located in the bottom of the Stephen P. Clark Government Center building.  Directly south of this is the main branch of the Miami-Dade Public Library System, as well as the HistoryMiami museum.  Henry Flagler's Florida East Coast Railroad owns roughly nine acres in the middle of Government Center, the site of its former Miami station, which spans several blocks.  While the station was destroyed in 1963 and the site had been used as surface parking lots in the decades following, the railroad never gave up ownership of the property.  In mid 2014, the lots were closed down for construction of a new Downtown Miami intercity rail station, as part of their All Aboard Florida system.

Downtown Miami Historic District: The Downtown Miami Historic District is a U.S. historic district (designated as such on December 6, 2005) located in the CBD of Downtown Miami, Florida.  The district is bounded by Miami Court, North Third Street, West Third Avenue, and South Second Street.  It contains 60 historic buildings.  A large portion the buildings in the historic district were built during the Florida land boom of the 1920s, when Miami experienced rapid population growth.  Many of the older structures from before the 1920s, were smaller scale buildings and homes from the Miami pioneer era of the mid and late-19th century.  Palm Cottage, built in 1897 is a home from the pioneer era that is still standing, however, few of these original homes remain.

BayLink: BayLink is a long proposed transit connection between Miami and Miami Beach, Florida.  Proposals have ranged from streetcar, light rail, monorail, Metromover, or Metrorail extension that would connect Downtown Miami to South Beach via the MacArthur Causeway, with the light rail or streetcar options potentially having loops at both ends.  Originally proposed as an elevated light rail line such as a monorail, Miami Beach city officials opposed this in favor of something less intrusive, such as a streetcar.  Historically, Miami Beach has also cited concerns of unwanted downtown residents as a detriment to the South Beach image.  Additionally, the unused parts of the bases of the MacArthur Causeway bridge pilings that were to be used to support the line have been used for the widening of the causeway for the construction of the Port Miami Tunnel, complicating a fully separated right of way.  Officials still thought it was feasible as a light rail streetcar, and in 2014 were considering the possibility of a public-private partnership to help fund it.  In 2015, the cities of Miami and Miami Beach decided to break the estimated $532 million system into three pieces; two compatible light rail loops in Downtown Miami and South Beach to later be connected via MacArthur Causeway.  This was motivated by the lengthy federal studies required for a larger project.  French transport vehicle manufacturer Alstom gave an unsolicited proposal to build the Miami Beach portion of the system for US$148 million as a wireless streetcar system from 5th Street to Dade Boulevard via Washington Avenue.  Alstom predicts over 20,000 riders a day just on the eight to ten stations that would be on the Miami Beach segment.

Epic Residences &amp; Hotel: Epic Hotel is an urban hotel and residential skyscraper in Downtown Miami, Florida, United States.  Epic is 601 ft tall and has 54 floors.  The tower is located on the north bank of the Miami River in Downtown Miami's Central Business District.  It is bordered by Biscayne Boulevard Way on the west, Southeast 2nd Street to the north, the Miami River to the south, and Southeast 5th Avenue to the east.  The architect of the complex is Revuelta Vega Leon.

Miami River (Florida): The Miami River is a river in the United States state of Florida that drains out of the Everglades and runs through the city of Miami, including Downtown.  The 5.5 mi long river flows from the terminus of the Miami Canal at Miami International Airport to Biscayne Bay.  It was originally a natural river inhabited at its mouth by the Tequesta Indians, but it was dredged and is now polluted because of its route through Miami-Dade County.  The mouth of the river is now home to the Port of Miami and many other businesses whose pressure to maintain it has helped to improve the river's condition.

Supporting paragraphs: Miami River (Florida) Greater Downtown Miami
Answer: 5.5 mi long