Lost technologies · Late Roman Empire · 4th century CE
The Lycurgus Cup
Roman glass that changes from green to red — thanks to nanoparticles of gold and silver.
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The Lycurgus Cup is a 4th-century Roman cage cup carved with the myth of King Lycurgus. In ordinary light it looks jade green; lit from inside, it glows ruby red. It is the only complete Roman object made from this kind of dichroic glass.
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Connected dossiers
The Antikythera MechanismComparable case · Ancient craft understood only with modern instruments.
Roman Concrete: The Self-Healing StoneSame era · Roman materials science.See The Lycurgus Cup in the discovery universe →
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How to read the labels
EstablishedSupported by strong, converging evidence.
ContestedEvidence exists but qualified scholars disagree.
UnresolvedThe question is open; evidence does not settle it.
LegendComes from myth, literature or tradition, not physical evidence.
SpeculativeA hypothesis with little direct evidence so far.
Hero image: The Lycurgus Cup lit from within, British Museum. Photo: Chappsnet · CC BY 4.0 · via Wikimedia Commons. Evidence labels describe the written claims, not the image. Version 1 · updated 2026-10-22.