BBC Latin America correspondent Richard Collings reports

Maria Reiche, a German mathematician, spent more than half a century investigating and protecting 16 mysterious ancient drawings known as the Nazca Lines over a 60 kilometre (45 mile) area in the Peruvian desert.

The drawings - believed to have been made between 700 BC and 900 AD - can only be fully seen from the air. They were declared a world heritage site in 1995.

Some look like alien figures and have led some science fiction writers to conclude they were built by interplanetary visitors.

The concentration and juxtaposition of the lines and drawings leave little doubt that they required intensive long-term work.

There appear to be two kinds of designs: the first are figures of various beings and things and the others form geometric lines. Maria Reiche concluded they were a giant calendar linked to the movements of the Sun, the Moon and the constellations.

She protected them from intruders by employing security guards paid for by the income from her writings.