Great empires like those in Central America, Asia and Europe from a bygone millenium.
I admire the educated scholars who are able to decipher ancient scripts, and the archaeologists who can postulate explanatory theories for the rise and demise of cities as they excavate and examine buried ruins.
Apparently we still do not understand why some of these flourishing cities of stone suddenly ceased to function.
The answers may still be lying buried in the rubble.
Copan and the Maya civilisation which declined in the 8th century.
Angkor Wat abandoned by the Khmer in the 14th.
Information which might just prove to be valuable to the architects and urban planners of the 21st century.
It is a monument to human ingenuity that cities like New York or London continue to operate as smoothly as they do.
I am awestruck by the technology, and the dynamics, and the sheer wonder of it all. Not only the skyscrapers, cathedrals and buildings of Government above ground, but the astonishing array of supportive engineering underground which provides the lifeblood for the living organism above.
Concrete foundations of enormous proportions, water and sewerage tunnels, pipes and pumps, electrical cable, telephone lines all constantly being repaired and renewed, rail and road tunnels.
All of the invisible infrastructure without which the city would die.
It is quite an extraordinary human achievement.
But I still occasionally worry about the Khmer and the Maya.