Spain's ingenious water maze Invented by the region's Moorish rulers 1,200 years ago, Valencia's irrigation system is now a model for sustainable farming. I It's early. Fingers of sunlight are only just starting to creep along the streets of Valencia's Old Town, but the stalls inside the city's Mercado Central are doing a brisk trade already. There's a queue at the charcuterie, and the man behind the counter is slicing wafer-thin strips of jamón serrano in double time. He zips from one customer to the next, ducking between stocky legs of ham that hang from the front of his stall like fatty windchimes. In the seafood section, tuna, sea bream, anchovies and huge pink langoustines glisten in the ice. One stall here specialises in snails; another sells only saffron.