WATCH: The world's best city to live in - and it's not in Africa

Six out of 10 of the Economist Intelligence Unit's least liveable cities for 2018 are located in Africa. 

Dakar, Senegal; Algiers, Algeria; Douala, Cameroon; Tripoli, Libya; Harare, Zimbabwe; and Lagos; Nigeria all feature on the list.

The remaining four cities in the bottom 10 are Dhaka, Bangladesh; Damascus, Syria; Karachi, Pakistan and Port Moresby, Papua New Guinea. 

The three best cities to live in, according to the index, are - in order - Vienna, Austria; Melbourne, Australia; and Osaka, Japan. 

It is the first time in the survey's history that Austria’s capital, Vienna, ranks as the most liveable of the 140 cities surveyed by the unit. Vienna displaced Melbourne from the top spot. 

Of the 140 cities surveyed, 49% registered negative changes in their overall liveability rank in the past six months and 34% experienced positive movements. The rest did not record any change, the unit said. 

According to the researchers, the cities that score best tend to be mid-sized cities in wealthier countries, and many cities in the top ten have relatively low population density.

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