Budapest, the capital of Hungary has 23 districts (Hungarian: kerület, pronounced [ˈkɛrylɛt]), each with its own municipal government.
[1] District I is a small area in central Buda (the western side), including the historic Castle.
To reach District IV, one must cross the Danube to find it in Pest (the eastern side), also at north.
No more districts remaining in Buda in this circle, we must turn our steps to Pest again to find Districts XIII, XIV, XV, XVI, XVII, XVIII, XIX and XX (mostly external city parts), almost regularly in a semicircle, going southwards again.
District XXI is the extension of the above route over a branch of the Danube, the northern tip of a long island (Csepel-sziget) south from Budapest.