🇬🇧 United Kingdom · Megalith
Swinside Stone Circle (Sunkenkirk)
Late Neolithic · Late Neolithic Cumbria (Langdale axe trade area)
55-stone porphyritic circle (28.6 m) above Duddon estuary — best preserved in North-West England.
🇪🇬 Egypt · Hydraulic works
Mons Porphyrites — Imperial Porphyry Quarry
Roman Imperial (29 BCE–211 CE, active to 4th c) · Roman Imperial
Mons Porphyrites (Gebel Dokhan) is the only imperial porphyry quarry in Roman Empire (29–211 CE) producing purple porphyry for Diocletian and Hadrian pillars, sarcophagi and Pantheon.