​From the industrial revolution until the 1920s, British people paid "knocker ups" to wake them. These were a common sight in places where people worked in shifts or at unusual times: when the own sense of time was overstrained to rouse by themselves. 

When the profession just began to evolve, knocker-ups used to rap or ring at the doors of customers. But neighbors complained – they were aroused unwantedly!  
 
To avoid this kind of disturbance, knocker ups then started using a long stick to tap on their clients' bedroom windows: loudly enough to wake those who paid them, but silently enough for the people living nearby to stay asleep. 
 
An interview with a female knocker up appeared in The Huron Expositor May 22, 1978. She tells she earned 30 to 35 shillings a week by serving around 30 houses or more a day.  
 
As Mrs. Waters explains, knocker ups were also employed by people who did own an alarm clock – but just like today, people got used to the sound of it and either slept through it or just switched it off and continued sleeping.  

L'Ossuaire Municipal in Paris holds the bones of about 6 million people. A small part of the 321 km long tunnel network has been a popular tourist attraction since 1874, but this subterranean museum was not exactly planned as being one. Rather, two threats for the city of Paris made it inevitable to create that what we know as the Catacombs of Paris today.

To explore the history of the catacombs, we have to travel way back to the first century, when Paris was occupied by the Romans and still called Lutetia. The Romans found there was limestone in the soil of the left bank of the river Seine, which is of perfect use for building walls. Up until the High Middle Ages, the limestone was acquired in open quarries outside the city walls. Then, in the 12th century, mining was replaced to underground workings. This had several advantages: deeper deposits could so be reached, and on surface level the soil could still be used for agriculture. When the city continued to grow in the 16th and 17th century, new underground quarries were developed and the old quarries were abandoned. Buildings, streets and neighborhoods of the expanding city were built over the quarries, that subsequently fell into oblivion.

But not for long. The Parisians again became aware of the existence of these underground galleries when houses and streets started to collapse in the late 18th century. These collapses were the result of the cave-in of the roofs of the 30 meter deep subterranean galleries, resulting in a chain reaction within the different layers of soil. The crumbling worked its way upwards and resulted in a collapse of the buildings on street level.

The most catastrophic collapse of this kind occurred in 1774 in the Rue D'Enfer, which ironically means 'Hell's street'. Indeed, the cavity which measured 30 meter in length as well as in depth reminded of a gaping entrance to hell. Pavements, buildings, even carriages and horses were swallowed by the gap. The limestone from the houses' walls returned to where it had come from.

Since the mining galleries where everywhere beneath the city, Paris was threatened to be go under completely...