This computer image provided Monday March 17, 2014 by the Press Office of socialist candidate to Paris Mayor Anne Hidalgo, shows a tunnel of abandoned railway from the 19th century, now ramshackle and overgrown, turned into a cinema. Hidalgo’s plan envisions not just a green space but in the tunnels, places for farming fish and mushrooms. (Photo by AP Photo/Anne Hidalgo's Press Office)

Tourists take “Velibs”, self service bicycles, on the Avenue Matignon in Paris, Friday March 14, 2014. The Paris mayor’s race will give the city a new leader for the first time in 13 years, and offers a chance to reimagine one of the world’s top tourist destinations. (Photo by AP Photo/Remy de la Mauviniere)

This computer image provided in March 2014 by Laisne Architectes shows an abandoned Paris subway station turned into a swimming pool, part of conservative candidate for Paris Mayor Nathalie Kosciusko-Morizet's, known as NKM, plan to reimagine the city. Paris has 10 abandoned metro stations, mostly unseen as the trains hurtle through their darkened tunnels. NKM has a futuristic plan to transform these stations into public spaces like a swimming pool, performance hall or restaurant. (Photo by AP Photo/Oxo Archiract/Nicolas Laisne Architectes)

This computer image provided Monday March 17, 2014 by the Press Office of socialist candidate to Paris Mayor Anne Hidalgo, shows a tunnel of abandoned railway from the 19th century, now ramshackle and overgrown, turned into a restaurant and aquarium. Hidalgo’s plan envisions not just a green space but in the tunnels, places for farming fish and mushrooms. (Photo by AP Photo/Anne Hidalgo's Press Office)

This computer image provided in March 2014 by Laisne Architectes shows an abandoned Paris subway station turned into a restaurant, part of conservative candidate for Paris Mayor Nathalie Kosciusko-Morizet's, known as NKM, plan to reimagine the city. (Photo by AP Photo/Oxo Archiract/Nicolas Laisne Architectes)

Tourists wait in line at the foot of the Eiffel Tower in Paris, Thursday March 13, 2014. Lines stretch for hours, leaving visitors to bake in the summer or soak in the rain for fear of losing their place. Socialist candidate for Paris mayor Anne Hidalgo wants to create an underground welcome area and rethink how people visit France's most popular monument. (Photo by AP Photo/Remy de la Mauviniere)

This computer image provided in March 2014 by Laisne Architectes shows an abandoned Paris subway station turned into a theater, part of conservative candidate for Paris Mayor Nathalie Kosciusko-Morizet's, known as NKM, plan to reimagine the city. (Photo by AP Photo/Oxo Archiract; Nicolas Laisne Architectes)

La Petite Ceinture, or the Little Belt, an abandoned railway from the 19th century, now ramshackle and overgrown is pictured Friday March 14, 2014. The Paris mayor's race will give the city a new leader for the first time in 13 years and is offering a chance to reimagine one of the world's top tourist destinations. Both candidates for Paris Mayor, Anne Hidalgo and Nathalie Kosciusko-Morizet, want to improve access to green spaces in Paris, where parks and playgrounds are rare in some neighborhoods and gardens tend to the formal. (Photo by AP Photo/Remy de la Mauviniere)

Tourists and Parisians enjoy the recently open promenade on the left bank of the Seine river in Paris, Friday March 14, 2014. Paris Mayor election candidate Anne Hidalgo wants to expand her predecessor’s walkway along the banks of the Seine and the newly fashionable areas around Paris’ canal district. (Photo by AP Photo/Remy de la Mauviniere)

This computer image provided in March 2014 by Laisne Architectes shows an abandoned Paris subway station turned into a gardenn, part of conservative candidate for Paris Mayor Nathalie Kosciusko-Morizet's, known as NKM, plan to reimagine the city. Paris has 10 abandoned metro stations, mostly unseen as the trains hurtle through their darkened tunnels. NKM has a futuristic plan to transform these stations into public spaces like a swimming pool, performance hall or restaurant. (Photo by AP Photo/Oxo Archiract/Nicolas Laisne Architectes)