Question: What is the name of the castle in the state where Štefánik's Observatory is located?

full_context: Document 1: Clam-Gallas Palace: The Clam-Gallas Palace () is a Baroque palace in Prague, the capital of the Czech Republic. The building is situated on the corner of Husova Street and Mariánské Square, in Prague Old Town. The palace was first designed by the imperial court architect Johann Bernhard Fischer von Erlach, from Vienna. It was built in 1714–18 by the Italian architect Domenico Canevale. During the rest of the 18th century, Jewish balls and concerts were held in the palace, and were attended by noteworthy artists including Mozart and Beethoven.
Document 2: Cubism: The leading Cubist architects were Pavel Janák, Josef Gočár, Vlastislav Hofman, Emil Králíček and Josef Chochol. They worked mostly in Prague but also in other Bohemian towns. The best-known Cubist building is the House of the Black Madonna in the Old Town of Prague built in 1912 by Josef Gočár with the only Cubist café in the world, Grand Café Orient. Vlastislav Hofman built the entrance pavilions of Ďáblice Cemetery in 1912–1914, Josef Chochol designed several residential houses under Vyšehrad. A Cubist streetlamp has also been preserved near the Wenceslas Square, designed by Emil Králíček in 1912, who also built the Diamond House in the New Town of Prague around 1913.
Document 3: Prague Castle: Prague Castle General information Architectural style Baroque and Mannerism Location 119 08 Prague 1, Czech Republic Current tenants Miloš Zeman, President of the Czech Republic and the First Lady Construction started 870; 1148 years ago (870) Completed 1929; 89 years ago (1929) Design and construction Architect Matthias of Arras and Peter Parler Website www.hrad.cz
Document 4: Štefánik's Observatory: Štefánik's Observatory (, obs. code: 541) is an astronomical observatory on Petřín hill in the center of Prague founded 1928 and named after Slovak astronomer Milan Rastislav Štefánik. Nowadays the observatory specializes above all in popularization of astronomy and related natural sciences.
Document 5: Embassy of Sweden, Prague: The Swedish Embassy to the Czech Republic is located on Úvoz street, in Hradčany, the castle region of Prague. It is close to the Strahov Monastery. The embassy has a great view of the rest of Prague because it is located up on the hill. A pedestrian path, named after Swedish diplomat Raoul Wallenberg, who saved thousands of Jews from the Holocaust, leads from embassy up to the Petrin Hill.
Document 6: San Pedro Valley Observatory: San Pedro Valley Observatory, originally called Vega-Bray Observatory is an astronomical observatory located on a small hill overlooking the San Pedro River Valley, just east of Benson, Arizona (USA). Founded in 1990 by Max Bray, an optician and Dr. Eduardo Vega, a pathologist, it is home to the Hoot-Vega Radio Telescope.
Document 7: Embassy of France, Prague: The Embassy of France to the Czech Republic is located on Velkopřevorské náměstí, in Malá Strana, Prague, next to Vltava's island Kampa. It occupies the large baroque Buquoy Palace (1719). The ground floor of the Embassy was flooded during the August 2002 floods.
Document 8: New Delhi: Jantar Mantar located in Connaught Place was built by Maharaja Jai Singh II of Jaipur. It consists of 13 architectural astronomy instruments. The primary purpose of the observatory was to compile astronomical tables, and to predict the times and movements of the sun, moon and planets.
Document 9: Miloš Zeman: Miloš Zeman (; born 28 September 1944) is a Czech politician serving as the third and current President of the Czech Republic since 8 March 2013. He previously served as Prime Minister of the Czech Republic from 1998 to 2002. As Leader of the Czech Social Democratic Party during the 1990s, he transformed his party into one of the country's major political forces. Zeman was Speaker of the Chamber of Deputies, the lower house of the Czech parliament, from 1996 until he became Prime Minister two years later in 1998.
Document 10: Eduard Stehlík: He graduated from the Faculty of Philosophy at Charles University, and has worked at the Institute for Military History since 1989, focusing on Czechoslovak military history. He has also cooperated with Czech television. He was declared an honorary citizen of Lidice on 27 October 2006.
Document 11: Praha Masarykovo nádraží: It was the first railway station in the city to serve steam trains, and the second oldest railway station in Prague, Czech Republic (the first is Praha-Dejvice, formerly Bruska on the Lány Horse-drawn Railway). The station was designed by Antonín Jüngling and came into service in 1845.
Document 12: Buchlovice Castle: Buchlovice castle (German: Schloss Buchlau) is a castle about west of Uherské Hradiště, in south-east Moravia, Czech Republic. Its history is closely connected with nearby Buchlov Castle which grew more and more uncomfortable in the late 17th century, and that is why Jan Dětřich of Petřwald decided to build a new castle. Buchlovice castle was built as a copy of an Italian villa in baroque style, by Domenico Martinelli. It is one of the most romantic buildings in this country. In 1800 it became property of the Berchtolds, and since 1945 the state castle is open to the public.
Document 13: Letná Park: Letná Park (in Czech "Letenské sady") is a large park on Letná hill, built on a plateau above steep embankments along the Vltava River in Prague, Czech Republic. Letná's elevation and location afford commanding views of the Prague Old Town ("Staré Město").
Document 14: Vyšehrad: Vyšehrad (Czech for "upper castle") is a historic fort located in the city of Prague, Czech Republic, just over 3 km southeast of Prague Castle, on the right bank of the Vltava River. It was built probably in the 10th century. Situated within the fort is the Basilica of St. Peter and St. Paul, as well as the Vyšehrad Cemetery, containing the remains of many famous people from Czech history, among them Antonín Dvořák, Bedřich Smetana, Karel Čapek, and Alphonse Mucha. It also contains Prague's oldest Rotunda of St. Martin from the 11th century.
Document 15: President of the Czech Republic: President of the Czech Republic Prezident České republiky Presidential Standard Incumbent Miloš Zeman since 8 March 2013 Style His Excellency Residence Prague Castle Seat Prague, Czech Republic Appointer Popular vote Term length Five years Renewable once, consecutively Inaugural holder Václav Havel 2 February 1993 Formation Constitution of the Czech Republic Salary 2,235,600 Kč ($86,830) Website www.hrad.cz
ground_truth: Prague Castle
sub_queries: Which state is Štefánik's Observatory located? Answer: Prague
what is the name of the castle in Prague Answer: Prague Castle