(see also museums below): Castle Rosenstein (1822–1830) Classical Württemberg Mausoleum (1824) which holds the remains of Catherine Pavlovna of Russia and King William I of Württemberg Wilhelma Zoo and Botanical Gardens (1853) The Observation Tower of Burgholzhof an 1891 brick observation tower constructed by the Cannstatt municipal architect Friedrich Keppler on behalf of the Verschönerungsverein Cannstatt e. V. ("Society for the Beautification of Cannstatt"), in the style of a Roman tower. Weissenhof Estate (1927), (International Style) Friedenskirche, a 1966 church using the 1892 tower of a bombed church The TV Tower (1950), the world's first concrete TV tower Stuttgart Airport Terminal Building, 2000. In neighboring Leinfelden-Echterdingen Parks, lakes, cemeteries and other places of interest At the center of Stuttgart lies a series of gardens which are popular with families and cyclists. Because of its shape on a map, the locals refer to it as the Green U. The Green U starts with the old Schlossgarten, castle gardens first mentioned in records in 1350. The modern park stretches down to the river Neckar and is divided into the upper garden (bordering the Old Castle, the Main Station, the State Theater and the State Parliament building), and the middle and lower gardens – a total of 61 hectares. The park also houses Stuttgart planetarium. At the far end of Schlossgarten lies the second Green U park, the larger Rosensteinpark which borders Stuttgart's Wilhelma zoo and botanical gardens. Planted by King William I of Württemberg, it contains many old trees and open areas and counts as the largest English-style garden in southern Germany. In the grounds of the park stands the former Rosenstein castle, now the Rosenstein museum. Beyond bridges over an adjacent main road lies the final Green U park, Killesbergpark or 'Höhenpark' which is a former quarry that was converted for the Third Reich garden show of 1939 (and was used as a collection point for Jews awaiting transportation to concentration camps). The park has been used to stage many gardening shows since the 1950s, including the Bundesgartenschau and 1993 International Gardening Show, and runs miniature trains all around the park in the summer months for children and adults. The viewing tower (Killesbergturm) offers unique views across to the north east of Stuttgart. On the northern edge of the Rosensteinpark is the famous 'Wilhelma', Germany's only combined zoological and botanical garden. The whole compound, with its ornate pavilions, greenhouses, walls and