The British Museum is an enormous facility dedicated to representing all cultures and all regions of human civilization.  It has on display a wide variety of examples of historical artifacts from the Greek, Roman, Viking and European Medieval eras including arms and armour.
British Museum
Famous Helmet from Sutton Hoo Burial
Recreation of the Sutton Hoo Helmet
Remnants of the Sutton Hoo Sword
Shield Fittings Found at the Burial
Viking Weapons
Viking Hoard
One-Piece Sallet
Rear View of Sallet
Chain Mail Standard
Bascinet Found in Africa
Open-Faced Bascinet
Greek Bronze Armour
Greek Bronze Helmet
Corinthian Helmet
Greek Helmet
Greek Helmet Other Side
Gladiator Helmet
Rear of Gladiator Helmet
Roman Footman Helmet
Crocodile Parade Armour of Roman Origin
Roman-era Weapons