Through its ability to make us dream and marvel at the achievements of the past, archaeology has evolved from an inconspicuous discipline based on ruins and fragments into one of the most attention-grabbing fields of scientific study today. Luckily for him, Eduard Seler had a weak constitution; in 1882 he met and married his doctor's daughter. Caecilie's energy and curiosity complemented Eduard's intellectual passion and capacity for hard, detailed work, and together they left Berlin for Mexico to decipher the codices of the Aztecs. These were the only authentic written accounts of the civilisation that weren't destroyed by the arrival of the Spaniards in the 16th century - and nobody had succeeded in interpreting them. Seler cracked the code of the Aztec calendar, which in turn revealed a great deal about their sacrificial rituals and their temple-building cycles; at the turn of every Aztec century, new, grander temples must be built over the old ones. Seler also realised that Aztec illustrations revealed the truth about Aztec education and everyday working lives. Meanwhile, Caecilie photographed their discoveries on their travels, and collected Aztec artefacts, found in far-flung rural markets. Today's archaeologists are making further important discoveries, like King Montezuma's secret room for communing with the gods, unearthed when a lift shaft in a Mexico City block was renovated. Today's scientists face the same challenge Seler knew - Mexico's capital city is built right over the ancient Aztec capital, so the opportunities to dig are limited and frustratingly brief. Ironically this fact, like his poor health, played to Seler's scholarly strengths and helped him become a giant in the story of archaeology.