Barcelona's mediaeval old town, today known as Ciutat Vella, is predominantly flat in appearance. However, a more detailed inspection reveals it to stand on a physical base of very uneven altitude, with numerous changes of gradient between high- and low-lying areas. In fact, the original core of the city, on which the Roman settlement of Barcino was built, is a small hill (Mons Taber) that rises above the rest of the old town. There are many urban toponyms in Ciutat Vella that indicate that the streets 'descend' from the top of the hill in all directions (from what would have been the Roman core down into the mediaeval quarters), and which usually receive the name baixada (Baixada de la Presó, Baixada de Santa Anna, etc.). Although this is the most significant of the toponyms, it is not the only one. Other names serve as 'indicators of the landscape': Pla de la Boqueria and Pla de Palau refer to flat urban spaces; Jonqueres and les Arenes, to low-lying depressions; and la Rambla, to the ancient hydrographic network. A toponym indicating a rise in altitude or a depression, as irrelevant as it may seem today, may historically have been significant, as it would have indicated whether the land was susceptible to flooding and, therefore, whether or not it was suitable for given activities. This study combines the qualitative approach characteristic of classical toponymic analyses with quantitative methodologies (specifically, LIDAR technology applied to Barcelona's physical environment), which we have employed before in other Mediterranean cities, such as Valencia. Keywords: urban toponymy, Barcelona, mediaeval town, landscape indicators.