We want to build sustainable and efficient tramway depots for the cities of the 21st century. Aim of TramStore21 is to resolve a typical challenge in urban areas: how to develop public transport infrastructures without increasing their negative impacts on the urban context. which impact their functionality. This is applied to the case of tramway stable and maintenance sites (depots). a rare and unfamiliar element of tram systems. but most fundamental for the public transport offer provided to citizens. Many wrong examples of depots have been observed across Europe. because of structural reasons explained hereafter: this lowered the capacity of tram networks. increased costs and negativities for tram operators and local communities. TramStore21 partners are tram owners (operators or authorities) already committed (see annexes) to (re)build depots. in Brussels. Rotterdam. Dijon and Blackpool. with support of a German industrial research institute: TS21 partners intend to cooperate. in order to avoid shortcomings and achieve excellent sustainable building cases. To do so. they will organize systematic share of know-how with external stakeholders and experts (other local institutions. economic and social actors. final beneficiaries). reviewing best and improvable practices relevant to tram depots. This will be done involving networks of technicians and urban practitioners from multiple profiles. Then. partners will be in better conditions to plan together each depot. and control that every step achieved by a partner complies with these higher standards of urban sustainability (social. economical. environmental). even when a single partner's know-how. means and context would have not allowed to reach them. TramStore21 finally aims to cross-examine respective contexts where this kind of buildings is being developed. looking at norms and market issues of relevance to partners. Achievements: TramStore21 book Discover the TramStore21 story through the project's book "Building sustainable and efficient tram depots for cities in the 21st century"! Who are the TramStore21 partners? What did they learn in this 5-year project? What do the tram depots look like? What are the sustainable features of these depots?http://www.tramstore21.eu/sites/default/files/brochures/Tramstore_Publication_ENG_DVD_v2.pdf