The agglomeration of Kathmandu has not yet been officially defined. The urban area of the Kathmandu valley is split among three different districts (collections of local government units within a zone) which extend very little beyond the valley fringe, except towards the southern ranges, which have comparatively small population. They have the three highest population densities in the country. Within the districts lie VDCs (villages), 3 municipalities (Bhaktapur, Kirtipur, Madhyapur Thimi), 1 sub-metropolitan city (Lalitpur), and 1 metropolitan city (Kathmandu). Some district subdivisions remain legally villages yet are densely populated, Gonggabu VDC notably recorded a density over 20,000 people/km2. (2011 census). The following data table describes the districts considered part of the agglomeration:

Answer this question, if possible (if impossible, reply "unanswerable"): How many districts make up the Kathmandu Valley urban area?
three