In one of the biggest days of activism, tens of thousands of people joined in a rally to put pressure onto the major super powers to address the issue of climate change. The activists have come from all over the world, from Sydney to Berlin, in order to unite everyone in fighting the threat of global warming at a summit in Paris.

Twenty-thousand pairs of shoes were laid outside the Place de la Republique in the French capital, which consisted of high-heels, boots and other forms of footwear, which was meant to symbolize absent marchers after attacks by Islamic State militants, which claimed the lives of nearly 130 people on Nov. 13 and also led France to ban the protest which was meant to be at the heart of the global action, according to Reuters.

Nearly 150 leaders are expected to arrive in Paris for the start of the U.N. climate change summit, which starts on Monday in the capital of France and aims at reaching a landmark global deal on limiting greenhouse gas emissions. The world's top three carbon-emitting countries - the U.S., China and India are scheduled to attend the opening day of the event, also known as COP21. Heavy security has been arranged for the summit amid the aftermath of the Paris attacks, but some activists refuse to be quiet, CNN reported.

Apart from lowering gas emissions, another goal of the summit is to help developing countries' economies so as to make them less reliant on fossil fuels. Essentially, the marquee goal of the Paris Talks is to keep the average global temperatures from rising two degrees Celsius, according to WIRED.