Main Image, by guest of nature
'Miracles And Wonders' by jesse treece
'Golden Door' by Mariano Peccinetti
'Portal' by Andres Gamiochipi
'Portal in the Woods' by Eugenia Loli
Above, by Caroline Alkire
Above, by Gareth Halliday
Above, Memory Hole, by Alex Coll
Above, Postcards from Tomorrow XII, by Alex Coll
Above, Tapping the Cosmic Tambourine, by Andres Gamiochipi
Above, Pipe Dreams, by KieranSperring
If it is where I think it is outside a university campus in the woods.
Even better! I'd like to think it's a real gateway to summon Satan made by drunken students