Simon Calder: Take a detour on the road to salvation

Should you ever start wondering about the point of wandering, set the controls for the heart of Europe: our alter Feind, the old adversary, Germany. Steer to one of its arteries, the A5 autobahn south from Frankfurt to Basel.

When the stretch south to Darmstadt opened in 1935, this was the world's first "proper" motorway, with limited-access junctions that kept the road clear for a life in the fast lane. For the 21st-century traveller whose lust for wandering has waned, the A5 provides access to a wealth of culture, landscapes and, well, wealth, at least in the Frankfurt area. It connects this dazzling city astride the Main with the shimmering heights of Heidelberg and the contrasting indulgences of Karlsruhe and Baden-Baden. Then it carves a corridor between the Black Forest and the Rhine, and ends at the Swiss border, on the brink of Basel's exuberance of art and architecture. But mostly you should go south to discover Germany's most magnificent Motorway Church.

The German language accords travel with more nobility than does English: the prosaic airline passenger becomes a Fluggast , a "flight guest", on Lufthansa. And motorists engaged in the mundane business of trundling through Germany can take exit 50 for inspiration, tranquility and solace.

The Rastplatz outside Baden-Baden has all the usual side industries associated with life on the road, plus a roadsign promising Heilige Messe, Holy Mass, each Sunday at 11am. The sign contains a pictogram of a traditional church, with nave and spire; but the reality is very different: a bulky pyramid that could, at a pinch, be concealing a Little Chef. But as the cross at the top reveals, it is actually the Catholic church of St Christopher, the patron saint of travellers. This is where the long and winding road to spiritual salvation intersects with the prosaic highway. It allows the motorist time to break free from the congested contraflow of modern life, and invites the hitch-hiker whose life is more stop than auto to pray for salvation from the roadside.

Autobahns, autoroutes and autostradas are good at connecting the wonders of the world, or at least Western Europe. But their basic elements – Tarmac and fumes and rubber and steel – displace the spiritual in favour of the mechanical. St Christopher's makes amends. According to the priest, Michael Zimmer, "In a time when speed, globalisation and competitive thinking puts many people under pressure, the church wants to offer a home".

The only human with whom I shared the space, and a few words, never told me his name but explained his mission: to light a candle for a friend who had been killed in a road accident a few weeks earlier.

The secular traveller will find plenty to make a stop for a philosophical fill-up. Like a latter-day Stonehenge, the orientation is no accident: each face of the pyramid is approached along an avenue of maples, aligned exactly with the compass points. The art is the work of a local sculptor, Emil Wachter, who is evidently happiest in concrete. His creations give the place an appropriate "under-construction" feel.

The works include a relief of a human figure with a car in place of a head; a portrait of Herod as a caricature of a South American dictator; and an unusual Last Supper, in which the Apostles seem to be helping a baffled Christ programme his sat-nav.

The idea, says Father Zimmer, is "To proclaim the message of God's inscrutable but nevertheless concrete presence." The Autobahnkirche may also provoke a more enlightened response to the traveller's eternal question of "where am I going?" than "a light industrial park outside Mainz".

Germany's green and pleasant town

Clean living is near to Godliness: head south from the Motorway Church on the A5 Autobahn to junction 63 to reach a suburb that transcends the motor car.

Three leafy kilometres south of the city of Freiburg, accessible by tram number 3, stands the quartier of Vauban. During the post-war occupation of Germany, this was the site of a French army barracks. But since 1993, it has been transformed into a sustainable community – and spruced up with paint in primary colours that gives a feeling of being in some ideological nursery school. Which, in a sense, you are.

Two wheels prevail over four, and solar panels are much more visible than parking spaces; some homes are so highly tuned that they generate more power than they consume. In the shops, local crafts and produce displace imported and pre-packaged goods; and the Wild Rose Free-spirit Centre offers the chance to confess for sins such as driving.