---
title: A Roman Cup Laced with Roman Nanotechnology and Five More British Museum Treasures That Kept Experts Guessing
description: The Lycurgus Cup turns from green to red. Discover it and five more British Museum treasures, from the Portland Vase to the crystal skull.
author: Dr Marina Nani (Editor-in-Chief)
date: 2026-10-25T10:19:16.970Z
updated: 2026-10-25T10:21:45.486Z
canonical: https://richtravelmagazine.com/article/british-museum-treasures-lycurgus-cup
image: https://cdn.nanimediahouse.com/front-of-4th-century-ce-roman-lycurgus-cup-british-museum-1958-1202-1.webp
categories: Food & Culture
content_type: Feature
region: London
publication: Rich Travel Magazine
schema_type: Article
about:
  - type: Organization
    name: British Museum
    description: National museum in Bloomsbury, London, showing the Bayeux Tapestry on loan from 10 September 2026 to 11 July 2027.
    url: https://www.britishmuseum.org
    industry: Museum
---

Under ordinary gallery light, the Lycurgus Cup looks like a carved block of jade, cloudy and green. Light it from behind and the same glass glows the deep red of a ruby. The cup has not moved and nothing has been added to it. Only the position of the light has changed, and that single shift has confounded historians and glassmakers for centuries.

The cup is one of six objects at the British Museum that hold far more than you see at first glance. Each one has a story of [craft, crime or deception](https://richtravelmagazine.com/article/the-real-italian-job-magnani-rocca-heist) behind it, and together they make a single morning's route through the building.

## 1. The Lycurgus Cup hides Roman nanotechnology in its glass

**Room 41**

Craftsmen in Alexandria or Rome made the cup between about 290 and 325 AD. It stands just under 16cm tall and belongs to a rare group of luxury vessels called cage cups, each carved from a single thick blank of glass. The carver ground away everything except a lacework of figures standing proud of the bowl.

The figures tell the story of Lycurgus, a king of Thrace who attacked Dionysus, the god of wine, and his followers. One of them, the nymph Ambrosia, escaped by turning into a vine. On the cup, that vine coils around the king and pins him in place while Dionysus, Pan and a satyr close in.

Electron microscopes finally explained the colour change in 1990. The glass is laced with particles of a silver and gold alloy around 70 millionths of a millimetre across, roughly a thousand times thinner than a human hair. The recipe holds only around 330 parts per million of silver and 40 of gold. Particles that small treat light in a way solid metal cannot: they scatter green light back towards your eye and let red light pass straight through. With the lamp in front of the cup, you see the reflected green. With the lamp behind it, you see the red that travels through the glass.

The makers almost certainly had no idea why their glass behaved this way. The gold may have arrived as a trace in the silver, which in Roman times usually contained a little gold, or as dust left on workshop tools. Only a handful of fragments of Roman colour-changing glass survive anywhere in the world, and the Lycurgus Cup is the only complete vessel.

Its own past is hazy. The cup first appears in print in 1845 and passed into the Rothschild family soon afterwards. The museum bought it from Victor, Lord Rothschild, in 1958. Its gilt metal rim and foot were added around 1800, and the museum has never removed them as the glass is cracked. Scientists are still borrowing from it: the same principle now drives sensors that change colour when they detect substances in a liquid, and a team in the Netherlands has reproduced the effect in a 3D-printed copy.

## 2. The Portland Vase was smashed into hundreds of pieces and rebuilt three times

**Room 70**

The Portland Vase is around 25cm tall and was made in Rome around the turn of the first century AD. A glassblower dipped a bubble of dark cobalt-blue glass into white glass and blew the two together. A carver then cut away the white layer, as a gem engraver cuts a cameo, to leave seven pale figures against the blue. Roman workshops produced cameo glass for only about two generations, and this is the finest piece to survive.

The vase surfaced in Rome in 1600, passed through the Barberini family and came to the Duchess of Portland in the 1780s. Her family lent it to the British Museum in 1810. On 7th February 1845, a visitor who later admitted he had spent the previous week drinking picked up a sculpture and hurled it at the case. The vase broke into [hundreds of fragments](https://richtravelmagazine.com/article/uncovering-titanic-s-lost-stories-jewellery-that-survived-the-sea-hearts-and-history). A museum restorer pieced it back together that same year, and the Duke of Portland declined to sue the man, saying he did not want the family to suffer for an act of folly.

The museum bought the vase in 1945 and has since taken it apart and rebuilt it twice more. In the last restoration, in 1988 and 1989, conservators fitted back chips that had been missing since 1845, filled the remaining gaps and matched the colours so closely that you will struggle to find the breaks. They expect the work to hold for up to 200 years.

The vase obsessed Georgian and Victorian Britain. Josiah Wedgwood spent years copying it in his jasperware and released his first edition in 1790. A Stourbridge glassmaker later offered £1,000 to anyone who could reproduce it in glass, and John Northwood finished his glass copy in 1876.

## 3. The Mold Gold Cape was beaten from a single ingot nearly 4,000 years ago

In 1833, workmen quarrying stone from a burial mound near Mold, in Flintshire, opened a stone-lined grave. Inside lay the remains of a skeleton wrapped in a crushed sheet of gold. The field had a name that now sounds like a prophecy: Bryn yr Ellyllon, the Hill of the Fairies.

The cape dates from between 1900 and 1600 BC. A goldsmith beat it out of one ingot into a seamless sheet, then worked rows of ribs and bosses into the surface to imitate strings of beads lying over folds of cloth. Between 200 and 300 amber beads once decorated it, and that amber had travelled from the Baltic. Only one bead reached the museum. The cape grips the shoulders so closely that its wearer could barely raise their upper arms, which points to ceremony rather than daily wear.

The British Museum bought most of the cape in 1836, yet pieces kept arriving for more than a century. The last fragments came in 1972 from a woman who wrote that they had belonged to her mother and had been dug up on her ancestors' land.

## 4. The Mechanical Galleon once sailed down a royal banquet table

**Room 39**

The gilded ship in Room 39 is a clock, a music box and a mechanical theatre in one. The Augsburg clockmaker Hans Schlottheim built it around 1585 for a princely court of the Holy Roman Empire. It stands just over a metre tall.

Three spring-driven clockwork motors inside the hull ran the whole show. The ship rolled along the table while a small organ played and drummers beat on a skin stretched across the base of the hull. Beneath the main mast, tiny electors processed past the Emperor on his throne. Sailors in the crow's nests struck the hours and quarters on bells, and a cannon in the bowsprit fired by itself. For guests who had never seen a machine move without a hand pushing it, the effect must have bordered on sorcery.

The collector Octavius Morgan gave the galleon to the museum in 1866. It no longer works: its wheels have been replaced with ball feet and its drum skin has gone. Schlottheim built sister ships, and the one at the Château d'Écouen, north of Paris, has been restored to working order.

## 5. The Holy Thorn Reliquary was stolen by the man hired to repair it

**Room 2a**

A Paris goldsmith made the reliquary in the 1390s for John, Duke of Berry, brother of the French king Charles V. It stands about 30cm tall and weighs around 1.4kg. Gold, enamel, rock crystal, pearls, fourteen rubies and two sapphires build a scene of the Last Judgement: God the Father at the top, Christ seated on a rainbow, the apostles around him and the dead rising from their graves at the base. At the centre stands a single blackthorn spike, believed to come from the Crown of Thorns that Louis IX of France brought from Constantinople in 1239.

The reliquary spent centuries in the Habsburg treasury in Vienna. Around 1860, the treasury sent it for restoration to Salomon Weininger, a Viennese dealer with access to skilled craftsmen. Weininger had a copy made, returned the copy and sold the original. Baron Anselm von Rothschild bought it before 1873, and his son Ferdinand left it to the British Museum in 1898 as part of the Waddesdon Bequest. When it arrived, its true identity had been lost and it was catalogued as Spanish work of the 16th century.

The swap came to light only in the 1920s. For decades the copy sat in the Vienna treasury, published and illustrated as the medieval original. Weininger never answered for this theft, but other frauds caught up with him: he was convicted in two trials and died in prison in 1879.

## 6. The crystal skull is a fake that fooled the museum for most of a century

**Room 24**

The life-size skull carved from rock crystal arrived in 1897, sold to the museum by Tiffany & Co of New York. It had first appeared in 1881 in the Paris shop of the antiquities dealer Eugène Boban, and for much of the 20th century the museum displayed it as a possible Aztec or Mixtec work.

Electron microscopes settled the matter. The surface carries the marks of a rotary jeweller's wheel, a tool unknown in the Americas before Europeans arrived, and the quartz probably came from Brazil, far outside Mexico's ancient trade routes. The skull was most likely carved in Germany in the late 19th century, when workshops in Idar-Oberstein were cutting imported Brazilian quartz. No crystal skull has ever been found in an archaeological excavation.

The museum kept it on display, now labelled as European and 19th century. When the skull was housed at the former Museum of Mankind, curators saw visitors fall into trances and speak in tongues in front of it. Bend down low beside the case and your own face lines up with the skull in the reflection on the glass.

## How to see all six in one visit

Entry to the permanent collection is free, and the galleries open daily from 10am to 5pm, with later opening on Fridays. Start on the ground floor with the Holy Thorn Reliquary in Room 2a and the crystal skull in Room 24, then head upstairs for the Portland Vase in Room 70, the Lycurgus Cup in Room 41 and the Mechanical Galleon in Room 39. The Mold Gold Cape usually sits in the prehistoric European galleries. Objects are sometimes moved or lent, so check the museum's online collection before you go.

If you book a timed ticket for the Bayeux Tapestry, on show at the museum until 11th July 2027, you can fold all six into the same day.