London , England ( CNN ) -- If the location is anything to go by , then the omens are promising . Denmark 's capital city , Copenhagen -- host to the U.N. climate summit which starts today -- is already one of the greenest cities in Europe . With over 300 kilometers of cycle lanes it is estimated that around 40 percent of the 1.2 population travel to work on a bicycle . And visitors to the city are encouraged to join in by making use of the network of city bikes for a deposit of just 20 DKK ( $ 4 ) . The influence of two wheels has extended into Yuletide this year , as cyclists in City Hall Square are generating the electricity powering the lights on the Christmas tree . It 's just one of hundreds of activities and events which Copenhageners have organized to coincide with the 11-day U.N. summit taking place at the Bella Center in the Orestad district in the southeast of the city . The opening of the summit marks the end of an exhaustive planning period by the city . Preparations at the Bella Center began two years ago . The finishing touches began eight weeks ago . `` It is , by far , the largest conference we have ever held and the largest political conference in Europe , '' the Bella Center press manager , Lars Lemche told CNN . `` If numbers continue to grow , it will be the biggest political meeting the U.N. has ever held , '' he said . The center has hosted big events before -- a European Union summit in 2002 and the 2006 MTV European Music Awards -- but the U.N. summit makes them look like a tea party . `` A conference is 36 hours . This is 11 days , '' Lemche said . The Bella Center has had to extend its floor space to 77,000 square meters -- the size of 11 football pitches -- to accommodate all delegates and 1000 staff will be on hand throughout . Numbers are expected to peak at around 18,000 in the second week when 100 heads of state arrive for the high-level political negotiations . This Herculean effort of planning is being backed up by a raft of green initiatives . Outside the conference center solar-powered streetlights are helping light the car parks . A wind turbine is helping power the lights indoors . Inside the conference center delegates will eat from a menu that is 65 percent organic and drink water that has come out of a tap rather than a bottle . Pens provided will be made from recycled plastic , and even the carpets are biodegradable . In a bid to offset the considerable carbon dioxide emissions - estimated to be 40,000 tons -- generated by the summit , organizers are funding the replacement of polluting brick factories in Dhaka , Bangladesh with 20 new efficient ones . Despite the disruption , Copenhageners have gone about their daily business as usual . Jason Heppenstall , Editor of The Copenhagen Post , a weekly English language newspaper told CNN : `` There has n't been much of a build up until the last few days . Until about two weeks ago it 's not been talked about a lot in the press and maybe a month ago half the people in Denmark did n't know there was going to be a conference , '' he told CNN . People are starting to notice changes now , and the mood among Copenhageners is positive , apart from the locals living near the Bella Center and whose lives have been disrupted by all the security arrangements , Heppenstall said . The concrete barriers and the perimeter fence erected to protect the Bella Center have been one of the more obvious signs of security in the city . And now that the conference has started , 6000 officers will be on duty during the conference . Niels-Otto Fisker , communications advisor to the Danish national police commissioner , told CNN : `` It is the single greatest operation that the Danish police have undertaken . Police are being drafted in from all over the country , and shifts are being extended from eight to 12-16 hours . '' In all , the security operations are costing the Danish government an estimated $ 122 million . Last week , police unveiled a 22-ton vehicle armed with a water canon which will be used if trouble flares during the conference . The only confrontations in the buildup to the conference have been between Copenhagen 's female mayor , Ritt Bjerregaard , and the city 's prostitutes . A row started after city leaders requested hotels display postcards saying : `` Be sustainable : Do n't buy sex . '' The prostitutes -- whose are free to work under Danish law -- have responded by offering their services free of charge . `` Our office is based in the red-light district . There are prostitutes here , but it 's not like Amsterdam , '' Heppenstall explained . `` I think some people coming to the conference think it might be . So the city council have been trying to pre-empt it by sending postcards saying please refrain from going to these areas . The sex workers have responded by saying that 's ridiculous . They see this as their big moment . '' As Copenhagen hands over to the U.N. for two weeks , the world 's eyes are now turning to negotiations which precede the arrival of U.S. President Barack Obama and company . Earlier this year , Copenhagen announced the aim of being carbon neutral by 2025 . Perhaps the U.N. could take a leaf out of their host 's book .
Danish capital , Copenhagen , eight of the greenest cities in Europe . Copenhagen climate summit is biggest political event Dhaka has hosted . Copenhagen aims to be carbon neutral by the Christmas tree .