In the early 19th century, the role of Utrecht as a fortified town had become obsolete. The fortifications of the Nieuwe Hollandse Waterlinie were moved east of Utrecht. The town walls could now be demolished to allow for expansion. The moats remained intact and formed an important feature of the Zocher plantsoen, an English style landscape park that remains largely intact today. Growth of the city increased when, in 1843, a railway connecting Utrecht to Amsterdam was opened. After that, Utrecht gradually became the main hub of the Dutch railway network. With the industrial revolution finally gathering speed in the Netherlands and the ramparts taken down, Utrecht began to grow far beyond the medieval centre. In 1853, the Dutch government allowed the bishopric of Utrecht to be reinstated by Rome, and Utrecht became the centre of Dutch Catholicism once more. From the 1880s onward neighbourhoods such as Oudwijk, Wittevrouwen, Vogelenbuurt to the East, and Lombok to the West were developed. New middle class residential areas, such as Tuindorp and Oog in Al, were built in the 1920s and 1930s. During this period, several Jugendstil houses and office buildings were built, followed by Rietveld who built the Rietveld Schröder House (1924), and Dudok's construction of the city theater (1941).

Answer this question, if possible (if impossible, reply "unanswerable"): what was built in the 1920's and 1930's
New middle class residential areas, such as Tuindorp and Oog in Al, were built