Design of green spaces located below the urbanised level. Themes, problems and solutions applied to a case study

The design of green areas and landscape is often related to spaces with special features, which, due to their territorial peculiarities, require the adoption of appropriate design solutions. This category includes spaces located below the urbanised/street level (or on different levels), which may have various origins: areas derived from the regeneration of defensive ditches that, after having lost their original function, have become centres of urban aggregation (ancient city walls, castles moats); sites derived from the demolition of buildings or other structures; spaces created expressly sub-level as a result of design choices. This paper deals with some design issues concerning those places, in relation to orography, vegetation and the type of users expected. Moreover, the opinion of the population is taken into account to clearly define design choices; the issue is explored using special techniques to involve citizens in the design process, namely focus groups and surveys aimed at identifying their needs. The paper, finally, presents a design experience applied to a study area in the municipality of Abbiategrasso (Lombardy region, Italy) located under the urbanised level and currently used as urban park (the so-called Fossa Viscontea). This park (about 3.7 ha) occupies the area of the ancient defensive moat of the historical village (including the Visconti Castle - 13^th century); design solutions are proposed for ensuring accessibility and fruition of this area such as leisure and aggregation centre.