One of his most beautiful buildings in Budapest is the Museum of Applied Arts. Another examples for Art Nouveau in Budapest is the Gresham Palace in front of the Chain Bridge, the Hotel Gellért, the Franz Liszt Academy of Music or Budapest Zoo and Botanical Garden. The second half of the 20th century also saw, under the communist regime, the construction of blocks of flats (panelház), as in other Eastern European countries. In the 21st century, Budapest faces new challenges in its architecture. The pressure towards the high-rise buildings is unequivocal among today's world cities, but preserving Budapest's unique cityscape and its very diverse architecture, along with green areas, is force Budapest to balance between them. The Contemporary architecture has wide margin in the city. Public spaces attract heavy investment by business and government also, so that the city has gained entirely new (or renovated and redesigned) squares, parks and monuments, for example the city central Kossuth Lajos square, Deák Ferenc square and Liberty Square. Numerous landmarks are created in the last decade in Budapest, like the National Theatre, Palace of Arts, Rákóczi Bridge, Megyeri Bridge, Budapest Airport Sky Court among others, and millions of square meters of new office buildings and apartments. But there are still large opportunities in real estate development in the city. Districts Most of today's Budapest is the result of a late-nineteenth-century renovation, but the wide boulevards laid out then only bordered and bisected much older quarters of activity created by centuries of Budapest's city evolution.Budapest's vast urban area is often described using a set of district names. These are either informal designations, reflect the names of villages that have been absorbed by sprawl, or are superseded administrative units of former boroughs. Such names have remained in use through tradition, each referring to a local area with its own distinctive character, but without official boundaries. Originally Budapest had 10 districts after coming into existence upon the unification of the three cities in 1873. Since 1950, Greater Budapest has been divided into 22 boroughs (and 23 since 1994). At that time there were changes both in the order of districts and in their sizes. The city now consists of 23 districts, 6 in Buda, 16 in Pest and 1 on Csepel Island between them. The city centre itself in a broader sense comprises the District V, VI, VII, VIII, IX and XIII on the Pest side,