Passports give us the opportunity to cross borders and discover new horizons, while keeping a record of our journeys throughout the world. As the first day of the "Week at Expo 2017" series, we celebrate the 50th anniversary of Expo passports and their continued popularity to this day.

Organisers of Expo 1967 Montreal first issued Expo passports as a novel form of ticket, with a separate page for each participating country to encourage visits to as many pavilions as possible. Visitors could either purchase an adult passport, or a youth passport. Shaped like a small booklet, these “passports” were sold at the entrance to the Expo site, and have since become one of the most popular souvenirs for visitors who want to keep track of all the different pavilions they visit.

Sixty years ago, on 6 July 1957, the “Interbau” international building exhibition – Expo 1957 Berlin - opened its doors to the public in Berlin's Hansaviertel neighbourhood. The Expo transformed the area into the popular district it is today, leaving behind a variety of masterpieces of modernist architecture.

Today, Hansaviertel is a central residential district and a preserved architectural and garden ensemble of West German post-war modernity. The entire collection of buildings constructed as part of Interbau received landmark status in 1995, and it is still considered as an illustrative example of mid-20th century architecture.

Fossil-fuel dependant transport accounts for nearly one quarter of worldwide CO2 emissions linked to energy, and the trend is set to increase as access to different forms of transport becomes more widespread in developing countries. This raises questions over the future of mobility: how will people move around cities, around countries, and across oceans in the future, in a sustainable manner?

Looking to the future, a potentially revolutionary form of transport is set to be available for visitors to Expo 2020 Dubai, the next World Expo. According to developers’ plans, an integrated Hyperloop system will be ready by the opening of the Expo to transport people and goods at supersonic speeds between Dubai and Abu Dhabi.

The intertwined relationship between food and energy is a fundamental question when considering future energy and future food supplies. The cultivation, processing, storage, packaging and transport of food accounts for a major share of energy consumption worldwide, of which an estimated 79% comes from fossil fuels.

Expo 2015 Milan – organised around the theme “Feeding the Planet: Energy for Life” – was an opportunity to address this challenge, which by its very nature impacts all countries and all people. The Expo was a platform for participating countries to exhibit the latest technologies regarding the production and consumption of food, and dealing with food waste. Participants thus demonstrated how feeding a growing population can be achieved in a sustainable manner, for example by economizing on land use and minimizing the energy-intensive practices of large-scale agriculture.

Strategically-placed vegetation can cut energy consumption by up to 50% and play a crucial role in filtering atmospheric pollutants in a city. Urban greening – planting living, green walls or roofs, wherever possible in urban spaces and cities - has become the trend for overcrowded cities, seeking to conserve energy and reduce air pollution and greenhouse gas emissions.

The concept, which has been around for over 2,000 years, combines nature and architecture, and has tremendous potential for improving energy efficiency in a city.