**1. Introduction**

Over the years, and especially since the Second World War, land transformation has become more and more intense, leading to the overexploitation of land and to the progressive recognition of its finite nature. More recently, the COVID-19 crisis has further warned us about the importance that a present and future sustainable built, as well as natural, environment, could have in facing unexpected emergencies more resiliently [1]. There is, therefore, an increasing need to find and adopt integrated solutions to make present and future development more sustainable [2]. Thus, it is essential for policy and decision makers to take careful decisions on urbanization and land use management, approaching the latter not only as a political and technocratic decision but as one that affects our society's well-being and quality of life [3].

This perspective is well acknowledged at the European level, with the European Union (EU) which, through time, has introduced a growing number of policies and actions aiming at promoting a more sustainable approach to development and urbanization [4]. In particular, the EU is trying to halt excessive land transformation with its objective to achieve zero net land take by 2050 [5] and, more recently, the European Green Deal has stressed the need to make Europe climate neutral by 2050 [6]. As a result, in the last few years, policy and decision makers at all territorial levels have started to dedicate increasing efforts to pursue urbanization and land use models that are more sustainable, thus leading to the consolidation of an increasingly heterogeneous set of interventions and practices aiming at this direction [7]. At the same time, it should be noted that this has happened from both the top-down and the bottom-up levels, in the context of both urbanized and depopulated remote rural areas [8,9].

Research and studies on sustainable urbanization and land-use have also increased through time, often stemming from different definitions and interpretations of "sustain-

**Citation:** Solly, A.; Berisha, E.; Cotella, G. Towards Sustainable Urbanization. Learning from What's Out There. *Land* **2021**, *10*, 356. https://doi.org/10.3390/ land10040356

Academic Editor: Jefferey M. Sellers

Received: 22 February 2021 Accepted: 23 March 2021 Published: 1 April 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

ability". When focusing on the use of land, the most recent definitions of sustainable urbanization perceive the latter as the "design of future urban development as well as the re-development of existing ones in an environmentally friendly and resource-efficient manner" [10] (p. 1). In particular, sustainable land use seems to depend both on the socio-economic processes that trigger spatial development and on the effectiveness of the instruments that regulate these processes [3]. Adopting a similar perspective, the recently concluded ESPON SUPER project (Sustainable Urbanization and land-use Practices in European Regions, 2018–2020; https://www.espon.eu/super (accessed on 15 March 2021)) reviewed the multiple approaches put in place in different European cities and regions towards the achievement of a more sustainable urbanization, bearing in mind that there are no "right instruments" or "right targets" that could possibly fit all territorial contexts, also due to the high heterogeneity that characterizes the European continent in terms of socioeconomic development, administrative culture and spatial governance and planning [11,12].

The present contribution builds on the results of the SUPER project to develop guidance for decision and policy-makers aiming at promoting a more sustainable urbanization of their territories. It does this through a critical analysis of the rich set of practices collected throughout the project and, in particular, exploring the variable degree of success that characterizes interventions aiming at different goals, as well as adopting different types of instruments. After this introduction, the second section introduces the theoretical framework of the SUPER project, before section three describes the methodology that it adopted to collect and analyze sustainable urbanization and land use practices throughout Europe. Section four constitutes the core of the paper; it provides a quantitative overview of the collected interventions, in particular in relation to their localization and degree of success, to then discuss more in depth their results in relation to their scope and objectives (i.e., densification, regeneration, containment, governance and sectoral policies), as well as to the types of instruments that they have employed (i.e., visions and strategies, rules and legal devices, land use regulations, programs and projects). Finally, a concluding section rounds off the contribution, summarizing its main messages and the implications for decision and policy makers and introducing a number of avenues for future research.
