I recently spent a week in the Basque country in northern Spain, about half of which was in the city of Bilbao. Bilbao is an example of something quite common in the modern world, which is an industrial city in which a lot of the industry has now gone away, which has gone through a period of post-industrial depression, and which is now rebuilding itself as a modern, services based city on top of the industrial ruins, if you like.

Bilbao appears to be doing a particularly good job of this. The new Bilbao Guggenheim art museum is a particularly beautiful piece of architecture (although it contains little interesting art). However, also central to the renaissance of the city is dramatically improved transport, and in particular a new metro system.

The design of this metro system has been influenced quite heavily by the unusual physical geography of the city of Bilbao. Bilbao is in the north of the Pyrenees, and extremely rugged country fronts onto the Atlantic ocean. Bilbao sits in the river valley of the Nervion river. The centre of the city is in a location a few miles up the river where the river loops back upon itself and there is therefore a sizeable flat area inside the loop of the river. However, the city's suburbs lie on the sides of the river and up the sides of a long river valley. The greater city is therefore a long, narrow, straight line.

What does this have to do with the metro? Well, it means that building a metro system to cover the whole city has one less dimension than is normally the case. It is only necessary to build a single line. The valley is sufficiently narrow that wherever people get off, they can walk in the direction perpendicular to the river to their destination.

Except there are two caveats.

Firstly, in the very centre of the city where the river loops back on itself, the valley is too wide for short walks to all destinations. This problem has been solved by simultaneously building a new tram line that follows the loop of the river, particularly to take people from the centre of town and metro stops to the Guggenheim museum.

Secondly, like with most port cities on rivers, there is a point below which there are no more downstream bridges. (As is also common with port cities, this is a fair way upstream, so that the river can be navigable a fair way upstream). At this point, the metro line forks, and has two branches parallel to each other on either side of the river. (One of these is not yet complete).

This works well, and does a fine job of connecting the downstream suburbs to the city upstream. Of course, what it does not do is bring people living on opposite sides of the river closer together. For that, some bridges do need to be built.

The metro system has a couple of other items of note. For one thing, rather than being at or below river level, in some cases the metro line has instead been dug inside the steep banks of the river. An interesting consequence of this is that whenever there is a side valley going off the main river valley, the metro line comes out of the side of a hill, goes through an elevated section over the tributary river, and then enters a hill on the other side of the tributary valley. It is quite spectacular.

Finally, the architecture of the metro system is nice. The stations were designed by Sir Norman Foster, and are spacious. It is a very non-claustrophobic metro system. (A lot of them are quite like the Canary Wharf tube station on the Jubilee Line in London, also designed by Norman Foster). The tunnels are wide, and its a very pleasant system to ride on.

Of course, none of this answers any questions about whether the system is economic. EU money has probably paid for a fair portion of it. However, as a piece of design it is very nice, and it demonstrates how much better the design of such things is today, even to those built only 20 years ago.