Where there was the village of Arse-durgui they built the city of Urgell (in Latin civitas Orgellia and in Catalan ciutat d'Urgell) and here lies the origin of the name Castellciutat.

The plain is called plana de la Seu and was formed by the Segre river.

Because it is located at one of the major crossroads of communication in the Catalan Pyrenees, la Seu d'Urgell has had a unique and historic role in the county of Urgell.

Parallel to the Valira river rises a mountain range, where stand the remains of two great fortresses, the Ciutadella and Ciutat Castle (in Castellciutat), both of historic importance in the town.

In the north, La Seu d'Urgell has borders with the municipality of les Valls de Valira, to the west with Montferrer i Castellbò where there is La Seu d'Urgell Airport (also known as Andorra-Pirineus airport), to the south-west with Ribera d'Urgellet, to the south-east with Alàs i Cerc, and to the north-east with Estamariu.

Despite the low population density of Alt Pirineu i Aran, the area hosts 6.6% of the exhibitions and other civic activities in Catalonia.

[15] In la Seu d'Urgell, there are numerous fairs and markets throughout the year: At its artificial whitewater course, Parc Olímpic del Segre, the town hosted the canoe slalom events for the 1992 Summer Olympics in neighboring Barcelona.