*3.3. Alvalade—the Trees as a Line vs. the Trees as a Volume*

At a time when the housing issue was sensitive, given the social changes caused by World War II that changed the urban reality of the city, the Alvalade neighbourhood, designed by Faria da Costa in 1944, proved to be experimental and innovative in the way it was conceived and then executed. The urban plan was promoted by the municipality, integrated in one of the biggest transformation areas north of Lisbon already planned in the Master Plan of Étienne de Groer (1938–1948).

The implementation of the urbanization plan for the area south of Avenida Alferes Malheiro was managed and partially assured by the State, thus defining specific areas for private construction. This situation favoured not only the introduction of the neighbourhood unity principle, but also the coexistence of different typologies of social housing with significant variations in building and public space design, as the current urban fabric still reproduces [18]. Therefore, the design of the Alvalade neighbourhood results from an articulated and rich set of ideas of urban fabric production where the urban layout, plot structure and building are an integral part of the design. If we consider the principles governing the execution plan, we can easily observe that they remain in the current structure of the neighbourhood: the nature, form and hierarchy of the urban layout; the eight housing cells and the road organization of each one of them; the exceptional elements that serve as articulation and focus of the urban layout; central public spaces in each housing cell, associated with school equipment and green spaces; the preponderance and diversity of the housing typology; and the coexistence of different urban models and experiences [18] (Figure 8).

The Alvalade neighbourhood is today a qualified space and a reference of diverse urban environments in the context of the city of Lisbon. We can, therefore, find spaces of great intensity of flows and activities, located along the main axes, as well as spaces whose vocation is almost exclusive of access to the dwellings and, therefore, of smaller flow.

In accordance with the ideals planned for this area, vegetation is highly present and takes form in various ways (Figures 10 and 11). Indeed, several effects are combined through tree and shrub alignments as well as occasional volumes of dense irregular vegetation to provide not only a distinctive place with its own identity but also a place of proximity.

**Figure 10.** The complex incidence of trees in the urban structure of Alvalade.

**Figure 11.** The diversity of formal relations between the tree and the street space in Alvalade.

One may note tree alignments, generally arranged for staging, emphasizing and framing a monument. That is namely the case of the alignments in Avenida da Igreja, developed in two parallel lines of trees (Figure 12, left). This alignment is reinforced by the presence of four *Cupressus semprevirens* in front of the church of São João de Brito. In other situations, namely in the "cul-de-sac" areas structured in "U's", vegetation is prominent (Figure 12, right). In these areas, tree alignments are combined with flower beds with all kinds of vegetation from shrubs to herbaceous and climbing plants. In this former situation, vegetation sets the boundaries of space, consolidating an urban identity through its textures. This example emphasizes that tree alignments are not always associated with streets of higher hierarchy. Indeed, in the case of Alvalade, tree alignments are identified in both structuring streets and housing impasses.

**Figure 12.** The tree alignments in Alvalade.

*Land* **2020**, *9*, 18

On the other hand, in the same neighbourhood, it is possible to identify aggregations of trees that adopt different languages, due to their more informal emplacements. In these cases, the trees are combined and arranged more organically and are often of distinct species, forming a dense green volume. In Alvalade, Bairro das Estacas and Avenida EUA (Figure 13), they assume a pioneering role in the city of Lisbon, as, amongst others, they are the first spaces that encompassed plantations of these characteristics, designed during the 1950s [19]. Today, it is possible to find other spaces in Alvalade of a more exceptional nature that adopt this system of trees aggregation in relatively dense volumes.

**Figure 13.** The trees as a volume in Alvalade.

Diversity may be the best word to describe Alvalade, not only in the multiple experiences of aggregation of built typologies but also of tree aggregation, of which the different tree alignments and the large green volumes of trees that fill the space between the buildings stand out unequivocally (Figure 14).

**Figure 14.** The trees as a line in Avenida da Igreja (above) vs the trees as a volume in Avenida EUA (below).
