Landesstraßen (singular: Landesstraße) are roads in Germany and Austria that are, as a rule, the responsibility of the respective German or Austrian federal state.
 The term may therefore be translated as "state road".
 They are roads that cross the boundary of a rural or urban district ("Landkreis" or "Kreisfreie Stadt").
 A "Landesstraße" is thus less important than a "Bundesstraße" or federal road, but more significant than a "Kreisstraße" or district road.
 The classification of a road as a "Landesstraße" is a legal matter ("Widmung").
 In the free states of Bavaria and Saxony – but not, however, in the Free State of Thuringia – "Landesstraßen" are known as "Staatsstraßen".
The Free State of Saxony (German: "der Freistaat Sachsen" ] ; Upper Sorbian: "Swobodny stat Sakska" ) is a landlocked federal state of Germany, bordering the federal states of Brandenburg, Saxony Anhalt, Thuringia, and Bavaria, as well as the countries of Poland (Lower Silesian and Lubusz Voivodeships) and the Czech Republic (Karlovy Vary, Liberec and Ústí nad Labem Regions).
 Its capital is Dresden, and its largest city is Leipzig.
The Carl-Zeiss-Gymnasium Jena is a state-funded German elite Gymnasium "(grammar school)" for highly gifted students in the fields of math, science, and technology.
 Before changing its profile to fully focus and these aspects, it used to be a regular German public Gymnasium with a special separate school section "(Spezialschulteil)" attached to it.
 The school is named after the famous optician Carl Zeiss and is located in the city of Jena in Germany "(federal state of Thuringia)".
 It admits students from all over the federal state.
The Free State of Thuringia ( ; German: "Freistaat Thüringen" , ] ) is a federal state in central Germany.
The 8th Cabinet of the German federal state of Thuringia, formed on December 5th, 2014, is the first cabinet of a German federal state being led by a politician of The Left.
 A so-called "red-red-green coalition", it is coalition of Die Linke, the SPD, and the Greens, and is headed by Bodo Ramelow.
 CDU|AfD serve as the government's opposition in the Landtag, which consists of 91 members.
Weimar (] ; Latin: "Vimaria or Vinaria" ) is a city in the federal state of Thuringia, Germany.
 It is located between Erfurt in the west and Jena in the east, approximately 80 km southwest of Leipzig, 170 km north of Nuremberg and 170 km west of Dresden.
 Together with the neighbour-cities Erfurt and Jena it forms the central metropolitan area of Thuringia with approximately 500,000 inhabitants, whereas the city itself counts a population of 65,000.
 Weimar is well known because of its large cultural heritage and its importance in German history.
Rettbach (Rot) is a river of Thuringia, Germany.
This list of the mountains and hills of Thuringia contains a selection of the mountains and hills to be found in the German federal state of Thuringia.
 They are arranged alphabetically with their height given in metres (m) above sea level ("Normalnull").
The Landtag of Thuringia is the parliament of the German federal state of Thuringia.
 It convenes in Erfurt and currently consists of 91 members of five Parties.
 According to the free state's constitution, the primary functions of the Landtag are to pass laws, elect the Minister-President and control the government of Thuringia.
Saxony-Anhalt (German: "Sachsen-Anhalt" , ] ) is a landlocked federal state of Germany surrounded by the federal states of Lower Saxony, Brandenburg, Saxony and Thuringia.

Question: Rettbach (Rot) is a river of Thuringia, a federal state in the central of which country?
Answer: Germany