The City of Pripyat  - Pripyat, Ukraine

After the disaster at the Chernobyl nuclear power plant the 50,000 residents of this city were forced to immediately evacuate. The city stands abandoned to this day.

http://en.wikipedia.org/wiki/Pripyat

Michigan Central Station - Detroit, United States

Built in 1913 this was once the tallest rail station in the world. Though at first a busy travel hub the station started to notice a decrease in passengers, eventually in 1988 this caused the station to be shut down for good.

http://en.wikipedia.org/wiki/Michigan_Central_Station  

Maunsell Forts  - United Kingdom

Created during WW2 by the British Navy these forts were made to deter and report German air raids on the coast. After the war, since they no longer serve a purpose they were abandoned.

http://en.wikipedia.org/wiki/Maunsell_Forts 

Six Flags New Orleans - United States

After being damaged during Hurricane Katrina this amusement park never reopened.

http://en.wikipedia.org/wiki/Six_Flags_New_Orleans

Wonderland - Beijing, China

What was planned to be the largest amusement park in Asia, now sits as an unsettling set of structures that spawn rumors and uneasy feelings among those who visit it, after construction was halted due to lack of funding.

http://en.wikipedia.org/wiki/Wonderland_Amusement_Park_(Beijing)

Tequendama Falls Hotel - Colombia

Built in 1923 as a symbol of the joy and elegance of the elite citizens of the 20s. This hotel was abandoned in 1950 due to river contamination.

http://en.wikipedia.org/wiki/Tequendama_Falls_Museum

Denbigh Asylum - Wales

Built in 1848 this mental asylum could house up to 200 patients before it was closed completely in 2002.

http://en.wikipedia.org/wiki/North_Wales_Hospital 

SS Ayrfield - Sydney, Australia

This 1,140-ton steamship that was built in 1911 assisted allied forces in both world wars and later became a cargo ship bringing supplies to and from various coastal cities before it arrived in its current location of Homebush Bay in 1972. After years abandoned, the ship has become a floating garden filled with plants birds and animals.

http://en.wikipedia.org/wiki/Homebush_Bay#Hydrography

Abandoned Mill - Ontario, Canada