Question: Wachau contains a tourist attraction that is on what river?

Context paragraphs:
Granite Island (South Australia): Granite Island, also known by the Ramindjeri people as Nulcoowarra, is a small island next to Victor Harbor, South Australia, about 80 km south of South Australia's capital city, Adelaide.  Although there are no permanent residents, there are buildings and shelters on the island, including a cafe.  It is a popular tourist attraction, particularly for people wishing to see little penguins (commonly called "fairy penguins") which live there.  The island also supported resident wallabies in the 1980s which captivated visiting tourists.  The island is accessible across a causeway from the mainland, either on foot or by catching an antique horse-drawn tram.  As of 2015, the private company Oceanic Victor intends to use the island as a departure point to ferry tourists to a new tourist attraction in adjacent waters.  Tourists will be able to enter an aquaculture seacage where they will be able to swim with and hand feed southern bluefin tuna, and observe other South Australian marine species.

Mystery Spot: The Mystery Spot is a visual illusion–based tourist attraction near Santa Cruz, California, opened in 1941 by George Prather.  Visitors of the Mystery Spot experience gravity-defying demonstrations on the short but steep uphill walk.  The Mystery Spot is a popular tourist attraction, and gained recognition as a roadside "gravity box" or "tilted house" illusion.  At this roadside attraction, the laws of gravity and physics seem to disappear as balls roll uphill and people lean over past their toes without tumbling over.

Cayman Turtle Farm: Cayman Turtle Centre is a conservation facility and tourist attraction located in the West Bay district of the Cayman Islands.  It is used for raising the endangered Green Sea Turtle.  Established in 1968 by a group of American and British investors as "Mariculture Limited", the centre was initially a facility used to raise the Green Sea Turtle for commercial purposes.  By raising the turtle in a farming operation, the investors could raise turtle-meat for consumption without depleting the wild population of the species.  Still in operation as a farm that breeds and raises turtles in order to sell product, the Cayman Turtle Farm has also become a research centre and tourist attraction.  Currently, the centre is a conservation project as well as the largest land-based attraction in the Cayman Islands.  The turtle centre welcomes more than 500,000 visitors annually.

Wachau: The Wachau (] ) is an Austrian valley with a picturesque landscape formed by the Danube river.  It is one of the most prominent tourist destinations of Lower Austria, located midway between the towns of Melk and Krems that also attracts "connoisseurs and epicureans" for its high-quality wines.  It is 40 km in length and was already settled in prehistoric times.  A well-known place and tourist attraction is Dürnstein, where King Richard the Lion-Heart of England was held captive by Duke Leopold V.  The architectural elegance of its ancient monasteries (Melk Abbey and Göttweig Abbey), castles and ruins combined with the urban architecture of its towns and villages, and the cultivation of vines as an important agricultural produce are the dominant features of the valley.

Dürnstein: Dürnstein is a small town on the Danube river in the Krems-Land district, in the Austrian state of Lower Austria.  It is one of the most-visited tourist destinations in the Wachau region and also a well-known wine growing area.  The municipality consists of the Katastralgemeinden "Dürnstein, Oberloiben" and "Unterloiben".

Mother Shipton's Cave: Mother Shipton's Cave (or "Old Mother Shipton's Cave") is at Knaresborough, North Yorkshire, England, near to the River Nidd.  Nearby is a petrifying well which is the oldest entrance charging tourist attraction in England, open since 1630.  The water of the well is rich in sulfate and carbonate which is deposited as a ramp and screen below, and in which artifacts are "petrified" (encrusted) as a tourist attraction.

Ausable Chasm (New York): Ausable Chasm is a sandstone gorge and tourist attraction located near the hamlet of Keeseville, New York, United States.  It is directly due west of Port Kent.  The Ausable River runs through it and then empties into Lake Champlain.  The gorge is about 2 mi long and is a tourist attraction in the Adirondacks region of Upstate New York.  It is fed by the Rainbow Falls at its southern extreme.

Sarasota Jungle Gardens: Sarasota Jungle Gardens has been a tourist attraction in Sarasota, Florida in the United States since 1936.  It offers ten acres, or four hectares, of botanical plantings along with bird and animal shows.  Special shows are held each December for the holiday season, including a classic "Punch and Judy" show, performed by "Professor DeWitt"  that has become an annual tradition during the past sixteen years.  Jungle Gardens is an old-fashioned, family-oriented tourist attraction that continues to appeal to the public.  It is open to the public for a per-use ticket fee, as well as offering yearly membership passes for those wishing to visit frequently.  Some children who visit regularly consider it their 'neighborhood park'.  Special events for children are held during the summer.  On a limited basis, the site is also available for special events that are compatible with the residential neighborhood that has grown up around it during its seven decades of existence.

Tourism in Burundi: Tourism in Burundi refers to tourism in Burundi.  Bujumbura is the capital city of Burundi which is also a major tourist attraction of the country.  In addition to this, Lake Tanganyika is a popular tourist attraction.

Boldt Castle: Boldt Castle is a major landmark and tourist attraction in the Thousand Islands region of the U.S. state of New York.  Open to guests seasonally between mid May and mid October.  It is located on Heart Island in the Saint Lawrence River.  Heart Island is part of the Town of Alexandria, in Jefferson County.  Originally a private mansion built by an American millionaire, George Boldt, it is today maintained by the Thousand Islands Bridge Authority as a tourist attraction.

Supporting paragraphs: Wachau Dürnstein
Answer: Danube