In a series of measures to tackle air pollution in the city, Madrid's City Hall has unveiled a highly-innovative and unconventional plan. The Spanish city says that it plans to plant mini gardens on rooftops of its public transportation busses and bus stops to boost its green credentials.

The proposed gardens are said to be self-sustainable, costing the city council around €2,500 each. 130 gardens will be installed around the city in the first stage of the plan. Busses on routes no. 27 and 34 will be the first to join the green revolution.

So, how are they different than regular busses?

The evergreen gardens installed on the busses' roofs will absorb CO2 emitted by the vehicles in traffic while also soaking up noise and heat. Thanks to photosynthesis, the plants will also clean the polluted air by producing oxygen while going around the city.

The city has been trying to improve the city's air quality after smog levels Roseto an alarming rate at the bustling Gran Via. Madrid City Hall had imposed restrictions on traffic in certain areas in December efforts to fight pollution.

The project, named "Muévete en verde", is a part of six proposals to transform the Spanish capital into a green example for the world.

However, Madrid isn't the first to come up with such an idea.

The idea of sustainable, eco-friendly busses was first introduced in 2010 by Marco Castro Cosio, a U.S.-based designer. He named his project "Bus Roots", and saidit aimed to reconnect urban communities with nature.Catalan landscape artist Marc Grañén had also designed similar busses in the Spanish city of Girona in 2013.

A year later, a public bus with a mini garden on its roof hit the road in Istanbul as part of a Project by the Istanbul Electrics, Trams and Tunnel Management (İETT).The bus - dubbed the "Botobüs," a combination made up from the words "botanic" and "bus" - started operations between Edirnekapı and Taksim in 2014.