Verulamium

Start with the grass beneath your feet. It is soft and even, with ducks calling from the lake below and the River Ver moving slowly past the reeds. Ahead, a low line of flint and tile rises out of the turf. It looks like an old garden wall. In fact, it is part of the boundary of one of the largest towns in Roman Britain, and you are standing inside it.

A quick word on location first. Verulamium sits in Verulamium Park, on the western edge of St Albans, a short drive east of Hemel Hempstead. Many visitors come over from Hemel for the day. The park, the remains, the museum and the cathedral on the hill all sit within easy walking distance of each other, so the whole story can be followed on foot.

Before the Romans, this valley belonged to a powerful British tribe called the Catuvellauni. Their settlement lay close by, and their leaders struck coins here. After the Roman conquest in the first century, a new planned town grew up beside the river. It had a regular grid of streets, timber shops and houses, and later a forum, which was the central square for markets and law courts.

The town also stood on Watling Street, a major Roman road that ran from the Channel coast through London and on to the north west. That road brought soldiers, traders and news. It also brought danger. Around the year 60, Boudica, queen of the Iceni tribe, led a great revolt against Roman rule. The Roman historian Tacitus records that her forces attacked this town after London and Colchester.

Here is the first surprise. Archaeologists have found a layer of burnt material from that attack, a dark band in the soil that marks the moment the early town burned. Verulamium recovered, though. Over the next two centuries it was rebuilt in more lasting materials, with masonry houses, painted plaster walls and fine mosaic floors. It became a confident and prosperous provincial town.

Now look closely at the wall in front of you. The core is flint, a hard local stone that breaks into glossy grey and black pieces. Running through it are flat bands of red Roman tile. Builders laid these courses to level the wall and hold it together as it rose. Where the facing has fallen away, you can see the rough rubble core. Once, these defences stood much higher and ran for a long way around the town.

Across the park is a small modern building that is easy to walk past. Go inside. It protects a mosaic floor and a hypocaust, which is the Roman system of underfloor heating. Hot air from a furnace flowed through gaps beneath the floor, which stood on short pillars of tile. You can look down on the geometric patterns of the mosaic, still lying where the Romans set them, in the room they once warmed.

On the far side of the park, the Verulamium Museum holds many of the finds from the town. This is where the mosaics really shine. One well known floor shows the head of a sea god, with claws of lobster rising from his hair. Another shows a scallop shell fanning out in soft colours. There are also wall paintings, pottery, jewellery and everyday tools that bring the ordinary life of the town into focus.

The second surprise lies across the main road, on private estate land. There you can visit the remains of a Roman theatre. Most people picture Roman entertainment as an amphitheatre for gladiators. This was different. It had a stage, and the audience sat on banked seating in a curve around it. Visible Roman theatres like this are rare in Britain. It usually needs its own separate visit, so check before you go.

Much of what we know comes from large excavations in the twentieth century. In the 1930s, the archaeologist Mortimer Wheeler and his wife Tessa Wheeler led major digs here. Later, in the 1950s, Sheppard Frere carried out further work. Their methods and records shaped how British archaeology was done for decades. Yet a great deal of the Roman town still lies under the grass and fields, never dug at all.

Now lift your eyes to the hill above the lake. The great building there is St Albans Cathedral. Its name comes from Saint Alban, who tradition holds was a citizen of this Roman town. According to the story, he sheltered a Christian priest and was executed for it on that hillside. He is remembered as Britain's first Christian martyr. The details come from later writers, so much of the story sits between history and legend.

Here is a link many visitors miss. When the medieval abbey church was built on that hill, its builders took materials from the ruins of Verulamium. Look at the cathedral tower and you will see many thin red Roman bricks set into the stonework. In a real sense, the old town climbed the hill and became part of the new one. The Roman city did not simply vanish. Its pieces were reused.

As you walk on, notice the gentle rise and dip of the land around you. Some of those bumps in the grass are buried walls and streets. Listen for the water, the children on the playground, the dogs on the paths. People have gathered in this valley for around two thousand years. Today they come for picnics and the lake. Take one more look at that line of flint and tile, and let it remind you what lies beneath.