When the detailed plan has entered into force, a plot subdivision is prepared in the area at the request of the landowner. The plot subdivision is a block-level plan on how the block will be divided into building sites. The preparation of a plot subdivision takes approximately 2.5 months. A separate plot subdivision or a change thereof is made at the written request of the owner of the area, if sufficient preconditions exist. At the request of the landowner, an experimental calculation may be carried out in the city-plan area. An experimental calculation is a proposal on the kinds of building sites that can be formed in the area. The experimental calculation map can be used, for example, as an attachment map to a deed.