St. Paul's Church, Frankfurt

Stand for a moment on the square and look at the walls. The stone is red sandstone, a warm, rusty colour that seems to hold the light even on a grey Frankfurt afternoon. The building is not tall and pointed like most churches. It is round, or nearly round, an oval drum with a single tower attached to one side. Around you, trams rattle past, and the cobbles of Paulsplatz carry the footsteps of office workers and visitors. This is Saint Paul's Church, and its shape is the first surprise.

The story begins with an older building. On this spot stood a Franciscan church, known locally as the Barefoot Friars' Church. By the late eighteenth century it was in poor condition, and the city decided to pull it down. Work on a new Lutheran church started in 1789, the same year the French Revolution began in Paris. Wars and money troubles then stopped the project for years. The church was only finished in 1833, more than four decades after the first stone was laid.

Why an oval? Lutheran worship puts the sermon at the centre. An oval hall lets a large congregation gather close around the preacher, so everyone can see and hear. It is a practical design, not a decorative one. But this practical choice had a consequence nobody could have planned. A room built for listening to one voice turned out to be a very good room for a large assembly. And in 1848, Germany needed exactly such a room.

In that year, revolutions spread across Europe. In the German lands, people demanded freedom of the press, civil rights and a united nation. There was no single German state at the time — only a patchwork of kingdoms, duchies and free cities. Elections were held, and in May 1848 several hundred delegates arrived in Frankfurt. They met here, inside this church. It became the seat of the Frankfurt National Assembly, the first freely elected parliament for all of Germany.

Imagine the hall in those months. The delegates were lawyers, professors, writers, clergymen and officials. Many of them were famous scholars, and critics later joked that it was a parliament of professors. They argued for hours about rights, borders and the shape of a future state. Spectators crowded the galleries, and the debates were reported across the country. The building was no longer a church in daily use. It was a political stage, and the whole nation was watching.

The Assembly produced a constitution in 1849. It included a list of basic rights for citizens — equality before the law, freedom of belief, freedom of opinion. The delegates offered the title of German Emperor to the King of Prussia, Frederick William the Fourth. He refused. He did not want a crown offered by an elected parliament. Without his support, the project collapsed. Troops dispersed the remaining delegates, and the revolution ended. For many decades, it looked like a failure.

Here is the second surprise. The work done in this room did not disappear. Ideas from the 1849 constitution shaped later German constitutions, including the Weimar constitution after the First World War. They also shaped the Basic Law of the Federal Republic, written after the Second World War. Many Germans see this building as the cradle of their democracy. A failed parliament, in the end, left one of the longest legacies in the country's political history.

The building itself did not survive the twentieth century intact. In March 1944, Allied air raids struck Frankfurt's old town. Saint Paul's Church burned, and only the outer walls were left standing. When you look at the sandstone today, you are looking at walls that survived that fire. The roof, the interior and the old galleries were all lost. The city around it was in ruins, and much of the medieval centre was gone.

After the war, Frankfurt made an unusual decision. This was one of the very first buildings the city chose to rebuild, before many homes and offices. Money and materials came from across Germany. The reopening was timed for 1948, the hundredth anniversary of the National Assembly. The architects, led by Rudolf Schwarz, did not try to copy the old interior. They created something simpler and more sober, suited to a country trying to begin again.

If the building is open when you visit, notice how you enter. The ground floor is low and fairly dim. You then climb stairs into the main hall, which is bright, high and almost empty of decoration. The architects meant this as a deliberate path — from darkness into light. Some people read it as a journey from war and dictatorship towards a democratic future. The plain white walls and the wide, calm space make that idea easy to feel.

Today the building is no longer used as a regular church. It serves as a place for ceremonies and public events. Each autumn, during the Frankfurt Book Fair, the Peace Prize of the German Book Trade is awarded here. Writers and thinkers from around the world have stood in this hall to give their acceptance speeches. In 1963, the American president John F. Kennedy also spoke here, during his visit to West Germany.

In the ring-shaped hall on the lower level, look for a large modern mural. It is a long painted procession of figures, showing the people's representatives moving forward together. The faces are not heroic or polished. They look tired, ordinary and very human. It was added in the early 1990s, and it is quite different in mood from the classical stone outside. Many visitors walk past it quickly, but it rewards a slow look.

Outside again, take a moment on Paulsplatz. The Römerberg, the old town square with the city hall, is only a short walk away. Behind you are modern buildings, rebuilt streets and the sound of the city at work. Look back at the red oval walls. They have held a congregation, a parliament, a fire and a rebuilding. As you walk on, the tower stays in view for a while — a quiet marker of an idea that took a century to arrive.