Why does the 'Leaning tower of Pisa' lean?

The Leaning tower of Pisa is one of the world’s most beautiful and bizarre buildings. It is the bell tower of the Cathedral of Pisa in Tuscany, Italy. The tower is Romanesque in style and made of white marble.

The tower at present leans about 14 feet from the vertical and continues to lean farther south every year. The structure, today more than 800 years old, has leaned almost since the day construction was started. It leans because when the building was half completed, the soil under one half of the circular structure began to subside and the tower tipped. After a gap of around 100 years, architects devised a plan to compensate for the tilt. Two storey’s, the third and the fifth where build out of line with the others and closer to vertical in an effort to alter the tower's center of gravity. But the leaning continued to increase gradually through the centuries. Pumping to keep water away from the surrounding ground and the injection of cement grout into the foundations and subsoil have been tried in recent years, but without much success. The tower continues to increase its tilt each year.

Why was it built? In 1174, during Pisa’s golden age, a period of economic prosperity and artistic riches, the citizens resolved to build the bell tower that their magnificent cathedral had been without for so long. The tower was to surpass all other towers being built in Italy at the time and was to symbolize the wealth and power of the illustrious Republic of Pisa.

From the top of the tower, astronomer and physicist Galilei, a native of Pisa conducted his famous experiments. He proved that bodies of different weight fall at the same speed.

References:

http://trifter.com/europe/italy/the-leaning-tower-of-pisa-why-does-it-lean/
http://www.endex.com/gf/buildings/ltpisa/ltphistory.html

Why the Dead Sea is called the 'Dead '?

It's called the Dead Sea because nothing lives in it. It is one of the saltiest water bodies in the world, almost six times as salty as an ocean. It is completely landlocked and gets saltier with increasing depth. Salt actually precipitates out and piles up on the bottom of the sea. White crystals of mineral salts cover everything on its shores. The water in it is deadly to many living things. Fish accidentally swimming into it get killed instantly. In fact there is no seaweed or plants or any kind of creature living in or near the water. But humans are remarkably adaptable. In fact our bodies are more buoyant in the Dead Sea, such that we can float on it as seen in the picture below. Reason is its high density because of high concentration of dissolved mineral salts. 

A natural question from an inquisitive mind will be - Why such high saline levels? The Dead Sea is continually fed water from the rivers and streams coming down off the mountains that surround it. But no rivers drain out of the Dead Sea. The only way water gets out of it is through evaporation. When the water evaporates, it leaves behind the dissolved minerals making it saltier.

There are few important uses of Dead Sea worth mentioning. It was one of the world's first health resorts and has been the supplier of a wide variety of products, - from balms for Egyptian mummification to potash for fertilizers. People also use the salt and the minerals from the Dead Sea to create cosmetics and herbal sachets.

References:
http://www.extremescience.com
http://en.wikipedia.org/wiki/Dead_Sea