The paving .... of Portugal...

Around Madeira and here.. in Portugal are what must be literally billions !! of these individual paving bricks... and whole roadways sometimes consist of them. I once did a movie of the skilled ''calceteiros'' tapping each one singly into the wet mortar by hand. The pattern seen here - where the black tiles meet the white - forms an illusion where the ground appears to form a 'hump' in the centre - when in actual fact the pavement here... is perfectly flat.