Avinguda Diagonal (Catalan pronunciation: [əβiŋˈɡuðə ðiəɣuˈnaɫ]) (in Spanish La Avenida Diagonal) is the name of one of Barcelona's broadest and most important avenues. It cuts the city in two, diagonally from west to east (by Barcelona's compass), hence the name.
It was originally projected by engineer and urban planner Ildefons Cerdà as one of the city's wide avenues, which along with Avinguda Meridiana would cut the rationalist grid he designed for l'Eixample (Catalan for extension). Both would meet at Plaça de les Glòries Catalanes, which Cerdà envisioned as the new city centre. However, Plaça Catalunya, equally a new addition to the city of Barcelona, and connecting Ciutat Vella and Eixample, and therefore occupying a more privileged position in the urban area, would finally become the centre. Avinguda Diagonal remains to this day a much-transited avenue and many companies and hotels use it as a privileged location, as can be seen in its architecture.
The avenue starts in the Les Corts district on the western edge of the city, and runs to the Sant Martí district on the eastern edge. To its west it connects with the Lleida-Madrid highway and Ronda de Dalt in the neighbouring municipality of Esplugues de Llobregat. To its east it meets the Ronda del Litoral on the border with the municipality of Sant Adrià de Besòs. It is consistently 50 metres (160 ft) wide and about 11 kilometres (6.8 mi) long.(Wikipedia)