At 1,248 km in length, this huge highway from Cadiz to Barcelona was the longest road in Spain. It is colloquially known as the Spanish Route 66, and many have travelled the entire route and written blogs about their adventure.
The N-340 predominantly runs along the coast, and has now been by re-classified in many sections by the Autovía A-7 and Autopista AP-7.
Since the N-IV occupies the single road access along the peninsular into Cadiz city, the 'Kilometre 0' of the N-340 is actually at the rather less romantic Tres Caminos industrial estate at Puerto Real near San Fernando. Nowadays, its first section is renamed the A-48; when this dual carriageway Autovíaends near Vejer de la Frontera,one can continue south on the N-340 to Tarifa and then east towards the port city of Algeciras.
Beyond Algeciras, the Autovía A-7 runs up the coast as far as Almeria. Many sections of the N-340 have been buried and upgraded to dual carriageways. At points, a service road alongside the highway is the original N-340. In other places, you can leave the A-7, which generally bypasses coastal towns, and take a more interesting route by following the old N-340 through the towns themselves, including Estepona, Marbella, Fuengirola, Benalmadena, Torremolinos and Malaga.
North of Malaga, the A-7 is an expensive and imposing new construction clinging to the mountainside through a series of viaducts and tunnels. You can follow the old coastal N-340 to Nerja, through Almuñecar, Solobreña, Motril and Adra, all the way into Almeria.
From Almeria, the N-340A cuts inland, heading west to Tabernas. The A-92 motorway follows the route, and leaving Andalucia it goes through Lorca, Murcia and Elche.
The road then branches off along the Rio Torremanzanas towards Alicante. Through traffic now takes the Autovía A-36. The road then heads inland, crossing a junction with the Autovía A-35 before traversing the Sierra de Benicadell through Alcoy. South of Valencia, the road becomes the Autovía V-31 and then reverts to the N-340 at junction 536 km of the A-7.
North of Valencia, much of the road has been superseded by the Autovía CV-10 and Autovía V-21 to Valencia. It eventually passes through Castellón de la Plana, before heading along the coast to Peníscola, changing to the A7 near Cambrils, crossing the River Ebro (delta) and continuing on towards Tarragona.
The road reaches Vilafranca del Penedès and crosses the Llobregat valley, including a junction with the Autovía A-2 and Autovía B-24.The road finally enters Barcelona, and winds through a series of suburbs and industrial areas with a variety of names. It is intermittently called; Carretera de Cadiz, later Carretera de Collblanc, then Carrer de Sants, Plaça d' Espanya, and Avinguda del Parallel, concluding its route at the Passeig de Josep Carner.