In 2023, the Sustainable Gardens in Plaza Mayor managed by Sierra, were announced as the winners of the Best Sustainability Action category at the AECC 2023 Awards. Plaza Mayor boasts ISO 14001, OHSAS 18001, BREEAM IN-Use (rating of «Very Good» for the Building and «Excellent» for Building Management) and accessibility certifications (Global Accessibility Standard UNE 170001-2).

Since 2010, the centre has been replacing its garden plants with native species that promote in-creased local biodiversity and require less irrigation.

Following the decrease in the use of aggressive chemical treatments, shrubs and trees serve as hotels for insects necessary for the garden. In addition, vertical gardens were installed with automated irrigation and the water used for irrigation is recycled through a treatment and recirculation system, reducing its consumption.