The father of Khmer architect Vann Molyvann said

 The father of Khmer architect Vann Molyvann said:

 1. Phnom Penh must expand to the south because it is a high land area, not flooded, easy to prepare sewage system, flood relief, high hills, less erosion, good soil for agriculture.

 2. Beware of the northern area because it is a lowland area prone to flooding.

 3. The east should be kept as a green area, the supply of green vegetables should not be allowed to expand in that direction, because the river upstream of the Mekong River is a source of clean water to supply the entire city, on the other hand, there is no source.  It is difficult to get sewage, prepare sewage system and discharge it.

 4. The west should be organized as a handicraft industry because it is easy to transport to the export port area, etc.