All around the spectacular razor-back ridge that the Incas built on, there are other warning signs: deep scars on the jungle-clad slopes left by landslides caused by natural erosion in the geologically young Andean mountains.
The mountain perch where the Incas established their homage to the gods of the Sun and the Moon is also split by no less than five geological faults.
The original inhabitants managed to stabilise most of these, even turning some into drainage channels, but they remain weak spots in the constructions, and most of the damage to buildings lies along those lines.
The National Institute of Culture which administers Machu Picchu acknowledges the problem, but it insists there is no need for panic.
"This is nothing new," said the Institute's executive director Ricardo Ruiz.
"The Incas were aware of just how unstable the region was when they started building 500 years ago. They were careful to protect the city when they built the foundations, and they did such a good job that there's very little damage to Machu Picchu until now," he added.
Mr Ruiz also attacked experts like Dr Kauffmann for being alarmist. "The geological process takes a very long time, and Dr Kauffmann knows this. In reality it takes 10 or 15 years to properly diagnose what's going on," he said.
"So for us to take radical action after a study that lasts just two or three months would be irresponsible," he added.
The Institute insists that it is determined to protect the spectacular ruins. Machu Picchu draws in some 700,000 tourists each year, easily winning the prize as Peru's biggest draw-card.
The Institute has plans to increase the numbers to nearly two million by 2005, and says it simply cannot afford to see anything happen to the site.
But Dr Kauffmann believes the institute is simply burying its head in the sand.
"I think the National Institute of Culture is acting irresponsibly. The solution isn't to hide the problem but to confront it, to see if the Japanese are right," he said.
"If they are not right, then we are okay, but maybe they are right. We can't afford to ignore them," he added.
Thursday, 29 March, 2001, 12:34 GMT 13:34 UK
1532-33 - Spanish conquistadores led by Francisco Pizarro defeat the Incas whose empire subsequently becomes part of the Vice-royalty of Peru with its capital in Lima.
1780 - Revolt against Spanish led by Tupac Amaru, who claimed to be descended from last Inca chieftain, fails.
1821 - General Jose de San Martin captures Lima from Spanish and proclaims Peru independent.
1824 - Peru is last colony in Latin America to gain independence from Spain.
1836-39 - Peru and Bolivia join in short-lived confederation.
1849-74 - Some 80,000-100,000 Chinese workers arrived in Peru to do menial jobs such as collecting guano.
1866 - Peruvian-Spanish war.
1879-83 - Peru and Bolivia are defeated by Chile during the Pacific War in which Peru loses territory in the south to Chile.
1884 - Chile given Peruvian province of Tarapaca in accordance with Treaty of Ancon.
1924 - Victor Raul Haya de la Torre sets up nationalist American Revolutionary Popular Alliance (APRA) in exile in Mexico.
1941 - Peru wins Amazonian territory following brief war with Ecuador.
1945 - Civilian government led by centre-left APRA comes to power after free elections.
1948 - Military government led by General Manuel Odria installed following coup.
1963 - Peru returns to civilian rule with centrist Fernando Belaunde Terry as president.
1968 - Civilian government ousted in coup led by General Juan Velasco Alvarado, who introduces populist land reform programme and carries out large-scale nationalisations.
1975 - Velasco ousted in coup led by General Morales Bermudez.
1980 - Peru returns to civilian rule with re-election of Fernando Belaunde as president; Shining Path, or Sendero Luminoso, guerrillas begin armed struggle.
1981 - Peru fights border war with Ecuador over Cordillera del Condor, which a 1942 protocol had given to Peru.
1982 - Deaths and "disappearances" begin to escalate following army crackdown on guerrillas and drug traffickers.
1985 - APRA candidate Alan Garcia Perez wins presidential election and begins campaign to remove military and police "old guard".
1987 - New Libertad movement led by writer Mario Vargas Llosa blocks plans to nationalise banks as Peru faces bankruptcy.
1988 - Peru seeks help from International Monetary Fund; Shining Path guerrilla campaign intensifies.
1990 - More than 3,000 political murders reported; independent centre-right Alberto Fujimori elected president on anti-corruption platform; severe austerity and privatisation programmes launched as inflation reaches 400%.
1992 - Fujimori suspends constitution with army backing; Shining Path leader arrested and sentenced to life imprisonment; new single-chamber legislature elected.
1993 - New constitution adopted, enabling Fujimori to seek re-election.
1994 - Some 6,000 Shining Path guerrillas surrender to the authorities.
1995 - Fujimori re-elected to second term; people convicted of human rights abuses pardoned.
1996 - Tupac Amaru guerrillas seize hostages at Japanese ambassador's residence.
1997 - Peruvian special forces free hostages held at Japanese ambassador's residence.
1998 - Border agreement with Ecuador.
2000 September - Peruvian spy chief Vladimiro Montesinos embroiled in scandal after being caught on film apparently trying to bribe an opposition politician.
2000 17 November - Peruvian human rights ombudsman's office says 4,000 people had "disappeared" since 1980 in war against left-wing rebels.
2000 20 November - President Fujimori resigns following political and financial scandals.
2000 22 November - Peruvian Congress sacks Fujimori and declares him "morally unfit" to govern; head of Congress Valentin Paniagua sworn in as interim president.
2001 2 March - Peruvian judge orders former President Fujimori, who has since fled to Japan, to appear in court on charges of dereliction of duty.
2001 April - Peru swears in new heads of the army, air force and navy after their predecessors resign over links to former President Fujimori.
2001 May - The president of the Supreme Court and nine senior judges are removed from their posts over alleged links with the fugitive former intelligence chief, Vladimiro Montesinos. The Peruvian deputy Treasury Minister, Alfredo Jalilie, resigns over allegations that he was instrumental in paying Montesinos $15m to leave Peru.
2001 June - Presidential elections are held. A centre-left economist, Alejandro Toledo, defeats the former president, Alan Garcia.
The ruins, about 40 kilometres (25 miles) from the Inca citadel of Machu Picchu, are in an area where an Inca army held out against the 16th Century invaders.
The expedition leader, British explorer Peter Frost, said the site was the biggest of its kind found since 1964 and could have been occupied by the Incas when they took to the hills after the Spanish conquest.
Feb. 4, 2002 -- South America's Andes Mountains, stretching for more than 5,000 miles from the southernmost tip of the continent to the Caribbean coast, are the last place on Earth humans occupied. Spreading south from North America, humans may not have reached the high peaks until as late as 18,000 years ago.
LIMA (AP) A car bomb exploded outside the U.S. Embassy in Lima, killing at least nine people and injuring dozens.
In the chaos following the blast last evening, the victims including at least two police officers and a young man wearing roller skates lay in the rubble-strewn street. Prosecutor Maria del Pilar Peralta said at least nine people were confirmed dead.