The following events occurred in architecture in the 4th millennium BC:
Sialk ziggurat near Kashan, Iran (3200BCE)
Ġgantija - megalithic temple complex on the island of Gozo (part of Malta, c.3600–2500 BCE)
Harappa - fortified city of the Indus Valley Civilization with as many as 40,000 residents (3300–1600 BCE)
Northern Europe
Céide Fields - oldest known field systems in the world, located in West Ireland
Brú na Bóinne complex - Neolithic passage tombs in County Meath, Ireland (c.3300–2900 BCE)
Knap of Howar - oldest preserved stone house in northern Europe, on the Orkney island of Papa Westray occupied from 3500–3100 BCE
Skara Brae - Europe's most complete Neolithic village located in the Bay of Skaill in Orkney, Scotland
Stonehenge - the earliest phase of the monument has been dated to about 3100 BCE
Sweet Track - oldest known engineered roadway located in Shapwick, Somerset, England (3806 BCE)
