As more cities are trying to incorporate greenery into urban living, green roofs have been sprouting up in different places, bringing with them benefits such as reducing flood risk, cooling buildings and providing places for nature to thrive.
Beehives in England can be found on top of iconic buildings such as St Paul's Cathedral and luxury department store Fortnum & Mason.
In 2015, a panel of UK urban experts predicted that cows will be grazing on top of London's skyscrapers by 2100.
Green initiatives, such as living walls, have sprung up around London. This living wall, built in 2013, reduces flood risk by capturing rainwater in storage tanks. The wall consists of 10,000 plants and is packed with over 20 seasonal species.
Milan's "Vertical Forest" is an award-winning skyscraper that was completed in 2014. More than 800 trees were planted on steel balconies with the aim of combating urban pollution.
A self-sustaining garden tower called 'Hyperions' was proposed by architect Vincent Callebau to be built near New Delhi, India. The design could allow occupants to grow vegetables on their balconies.
CityTree is a mobile installation which removes pollutants from the air, shown here in Brussels. Berlin-based Green City Solutions claim their invention can capture as many pollutants as 275 trees.
This rooftop farm in Cape Town, South Africa, was built by a non-profit micro-farming organization called Abalimi and aims to provide crops for underprivileged groups and communities.
A rooftop farm on airline Cathay Pacific's headquarters in Hong Kong opened in 2016 to give staff the opportunity to grow their own food close to their office. Over 50 varieties of vegetables and herbs were planted.
Singapore was named the "greenest city in Asia" in 2018 in the Green City Index. This apartment block features a rooftop garden for its residents -- an example of efforts to incorporate nature into urban life.
Last month, urban greenery specialist GWS Living Art launched the 'Garden on the Move' campaign and installed green roofs on 10 public buses in Singapore.
'Garden on the Move' is part of a trial to see whether plants can help to reduce the temperatures inside buses so that operators can save the fuel that is spent on air conditioning.
The plants are succulents and grasses that have been specially selected to withstand warm conditions on top of the buses.
The same technology has been used in other parts of the world, including this bus stop in Kuala Lumpur, Malaysia. The plants reduce the temperature and purify the air around the bus stop, as well as providing a home for city wildlife. According to GWS LIving Art, the bus stop can survive 7-10 days without water.
In Rotterdam, a floating green park made entirely from recycled plastic found in the harbor has been developed by the Recycled Island Foundation. The park serves as a green space for people and a home for nature, including fish and birds.
The Recycled Island Foundation estimates that 12,000 kilos of plastic was used to build the 40 square meter floating park. Plastic was collected in litter traps like this.