Question: Kettenbrücke-Walzer commemorated the construction of the first chain bridge over a river located in which part of Europe ?
Context: State Route 123 (SR 123) is a primary state highway in the U.S. state of Virginia.  The state highway runs 29.27 mi from U.S. Route 1 (US 1) in Woodbridge north to the Chain Bridge across the Potomac River into Washington from Arlington.  It goes by three local names.  From its southern terminus to the Occoquan River Bridge, it is known as Gordon Boulevard.  From the Occoquan River Bridge to the city of Fairfax it is known as Ox Road.  North from Fairfax, it is known as Chain Bridge Road.  SR 123 is a partial circumferential highway in Northern Virginia that connects Woodbridge in eastern Prince William County with the independent city of Fairfax and the Fairfax County communities of Vienna, Tysons Corner, and McLean, the last the home of the National Counterterrorism Center and the Central Intelligence Agency.  The state highway also connects all of the major highways that radiate from Washington, including Interstate 95, I-66, US 29, US 50, SR 267, and the George Washington Memorial Parkway.  Furthermore, SR 123 crosses another pair of circumferential highways, I-495 and the Fairfax County Parkway, and SR 7, a major northwest–southeast highway through Northern Virginia.  The state highway is a part of the National Highway System for its entire length. The Deutz Suspension Bridge (German: "Deutzer Hängebrücke" ) was a self-anchored suspension bridge using eyebar chains, across the Rhine at Deutz in Cologne, Germany.  It was built from 1913 to 1915.  In 1935, it was named Hindenburg Bridge after Germany's second President deceased the previous year.  It collapsed on 28 February 1945 during repair works and was replaced in 1948 by the world's first steel box girder bridge designed by Fritz Leonhardt and Gerd Lohmer.  H. D. Robinson, who later worked with David B. Steinman on the Florianopolis Bridge, another eyebar chain bridge, consulted on the towers for the design of this Cologne bridge.  It reportedly later served as inspiration for American bridge engineers and was specifically cited as a design influence on the Three Sisters bridges in Pittsburgh, Pennsylvania as well as for the Kiyosu Bridge on the Sumida River in Tokyo. Clara Barton Parkway is an automobile parkway in the U.S. state of Maryland and the District of Columbia.  The highway runs 6.8 mi from MacArthur Boulevard in Carderock, Maryland, east to Canal Road at the Chain Bridge in Washington.  Clara Barton Parkway is a two- to four-lane parkway that parallels the Potomac River in southwestern Montgomery County, Maryland, and the far western corner of Washington.  The parkway provides access to the communities of Cabin John and Glen Echo and several units of the Chesapeake and Ohio Canal National Historical Park.  The Maryland portion of the George Washington Memorial Parkway was constructed from Carderock past Interstate 495 (I-495) to Glen Echo in the early to mid-1960s.  The parkway was proposed to continue west to Great Falls and east to Georgetown.  However, these proposals never came to fruition and the parkway was extended only to the Chain Bridge in the early 1970s.  The Maryland portion of the George Washington Memorial Parkway was renamed for Clara Barton, the founder of the American Red Cross, in 1989. The Chain Bridge (German: "Kettensteg" ) is a pedestrian chain bridge in Nuremberg, Germany.  The bridge crosses the river Pegnitz just a few meters upriver of Fronveste and Schlayerturm, fortifications in the course of the medieval city wall guarding the river's exit from the town.  It connects Maxplatz in Sebalder Altstadt (the old quarter north of the river) with Untere Kreuzgasse in Lorenz, the quarter on the south side of the river. The Chain Bridge in Newburyport, Massachusetts, is a "look-alike" replica built in 1910 to replace the "first suspension bridge" constructed in the United States in 1810.  Since the current structure is one of a series of bridges at this location since 1793, it is "the oldest continually occupied, long span, bridge crossing" in the US.  It has also been called the Essex-Merrimac Bridge or Newburyport Chain Bridge. The Danube ( , known by various names in other languages) is Europe's second-longest river, after the Volga River.  It is located in Central and Eastern Europe. The Chain Bridge is a viaduct which crosses the Potomac River at Little Falls in Washington, D.C. It carries close to 22,000 cars a day.  It connects Washington with affluent sections of Arlington and Fairfax counties in Virginia.  On the Washington side, the bridge connects with Canal Road.  Left turns onto the Clara Barton Parkway from the Chain Bridge are prohibited, but the reverse is permitted.  On the Virginia side, the bridge connects with State Route 123 (Chain Bridge Road), which provides access to the George Washington Memorial Parkway. The Chain Bridge Road School is an historic school, located at 2820 Chain Bridge Road, Northwest, Washington, D.C., in the Palisades neighborhood. Kettenbrücke-Walzer ("Chain Bridge Waltz"), opus 4, is a waltz composed by Johann Strauss I in 1828.  Its title commemorated the construction of the first chain bridge over the branch of the Danube through the inner city of Sophiebrücke in Vienna.  The composition employed the instrumentation of: one flute, two clarinets, two horns, timpani, three violins and double bass. The Union Bridge, also known as the Union Suspension Bridge or Union Chain Bridge, is a suspension bridge that spans the River Tweed between Horncliffe, Northumberland, England and Fishwick, Berwickshire, Scotland.  In so doing it also spans the border between England and Scotland.  When it opened in 1820 it was the longest wrought iron suspension bridge in the world with a span of 137 m , and the first vehicular bridge of its type in the United Kingdom.  Although work started on the Menai Suspension Bridge first, the Union Bridge was completed earlier.  Today it is the oldest suspension bridge still carrying road traffic and is a Category A listed building in Scotland and a Grade I listed building in England.  It lies on Sustrans Route 1 and the Pennine Cycleway.
Answer: Central and Eastern Europe