It is said that the medieval era never really ended in Nepal, its historic towns and architectural jewels blessed by an unbroken continuity of life and ritual that links the present with the past. The lasting image for tourists flying out of Kathmandu is of the multi-roofed pagodas of palaces and temples and the 16th century courtyards, which were once the basic unit of city planning.But much of the capital\'s ancient architecture will soon be no more than a memory, according to one of the world\'s leading authorities, Niels Gotschow, as haphazard urbanisation and a desire for modernity change Kathmandu.\"To put things into a book is an act of preservation because one day this will be the only way to remember,\" says Gutschow, who has dedicated the last four decades to chronicling and preserving Nepal\'s architectural treasures. Gutschow, 70, has pulled up countless floors and chipped endlessly at concrete to reveal the long-lost craft of the Newars -- the Kathmandu Valley\'s indigenous inhabitants renowned for their striking brickwork and wood carving.The Hindu and Buddhist monuments of the three cities of the valley on which the German national has worked -- Bhaktapur, Kathmandu and Patan -- were collectively designated as the first Asian UNESCO World Heritage Site in 1979.But every year bahal courtyards with richly-carved doors are demolished, balconies and lintels removed, and cornices and roof struts pulled down to make way for new homes in the fast-expanding capital.Significant monuments, monasteries, temples and historic houses across the valley are being lost in their entirety.\"Until ten years ago a person did not even need a demolition permit,\" says Gutschow. \"So you\'d demolish your house, even in the so-called World Heritage Sites.\"An amendment of the law now requires a demolition permit but that doesn\'t mean much. There\'s no enforcement because no municipality can ask the (authorities) to send a policeman to enforce the law. It\'s a lawless country.\"Born in Hamburg, the son of an architect, Gutschow studied architecture at the University of Darmstadt and spent time as an apprentice carpenter in Japan in the 1960s.He came to Nepal in 1971 to volunteer on the restoration of the Pujari Math Hindu monastery in Bhaktapur, a Newar city around 13 kilometres (eight miles) east of Kathmandu where he made a home with his wife, Wau. Gutschow\'s stock-in-trade is rescuing historical buildings from ruin with a holistic approach that takes account of ancient rites and building techniques, relying on old photographs and historical detective work.His latest project is on the restoration of the Patan Royal Palace and the Bhandarkhal Archaeological Garden, a trove of buried archaeological treasures dating back to the 12th century.But local communities, preoccupied with moving towards a decent standard of 21st century living rather than preserving medieval character, are not always appreciative of his work.He recalls the at times violent resistance to his conservation efforts, particularly over the Itum Bahal, one of the largest Buddhist courtyards in Kathmandu, where his workers were attacked with hammers. He says his work is about documenting a period which is largely beyond salvation. But while the last Newari house may be gone in a generation, he is trying to preserve the \"key monuments\" of Kathmandu.\"Architecture of Newaris\", Gutschow\'s three-volume labour of love 40 years in the making and the latest in a canon of work stretching to more than a dozen books, was published at the end of last year.It is the \"ultimate\" chronicle of Newari building techniques, says Gutschow, but it may soon also be the only record of an age consigned to history by the thrust for modernity.\"I do not get depressed,\" he says. \"It\'s part of life.\"