More than half the world's population now lives in cities.
How to house and feed millions of people, power their homes and businesses and move them from place to place while reducing environmental impact and combating climate change are among the challenges now under the spotlight.
That's where Smart Cities come in. A smart city is basically one where data and sensors are used to plan and deliver better public services, and where everything is connected.
This could involve analysing travel patterns to help reduce congestion and improve public transport systems.
Sensors in rivers can be used to monitor water levels, helping to warn about flooding and help city bosses quickly plan a response. Energy consumption in buildings is measured to help improve efficiency and reduce emissions.
Part of the Smart City concept also includes constructing environmentally-friendly buildings which use less water and power, provision of a good public transport system and cycling routes, excellent communications infrastructure, including wifi and using efficient public lighting.
But is Dublin smart?
Finding where the capital is ranked on a global scale is difficult, as there are few indicators available. One, from IESE Business School at the University of Navarra in Spain, ranks Dublin as 36th in the world. But what does that mean?
"There's a lot of work being done to develop a proper index, but it's not straightforward," Smart City programme manager in Dublin City Council, Jamie Cudden said. "There's a group of cities recognised as being smart, like Amsterdam, Copenhagen and Barcelona and Bristol and Greenwich in the UK. But it comes back to what your view of what smart is."
A survey last year, 'Your Dublin, Your Voice' included a question on "city perception". It found that 45pc of respondents believed that Dublin was a "smart" city, but this perception was lowest among students.
The lack of tech investment for the public good, coupled with a poorly-integrated public-transport system and poor broadband were cited as the main reasons why it wasn't up to scratch. Conversely, the presence of so many IT companies, the educated workforce and use of technology and apps for services were seen as positives.
Dublin's advantage is that so many hi-tech firms are located here, including Google, IBM, Intel and Microsoft, all of which work in this space.
The city has also made strides installing hi-tech solutions to everyday problems.
Need to know when a bus, train or Luas is coming? Online apps and real-time passenger information tell you. Using a Leap card also reduces the need for cash for fares, while offering better value.
The city centre offers free public wifi, and its sophisticated traffic system allows congestion and traffic flows to be monitored in real time, thereby allowing planners to adjust traffic signals and give public transport priority at busy times.
In addition, low-cost sensors developed by Kingspan are installed across the city to gauge water levels, while smart bins in Dun Laoghaire alert the council when bins are full. In Croke Park, sensors dotted at the entrance help gather data on crowds.
Research projects are under way, including one between UCD and IBM to research how smart buildings will reduce running costs and provide environmental wins through better energy systems, lower water usage and better transport solutions.
NUI Maynooth has also been given €2.3m in funding for a five-year project, The Programmable City, to analyse how technology can influence life in the city.
But key to all of this is the availability of data. The Programmable City has compiled the Dublin Dashboard (www.dublindashboard.ie) which gathers data from a range of sources and sets out what's happening across the city in real time. There's alerts on water cut-offs, travel times on the M50 and city streets and data on available car parking spaces.
But there's also data on planning applications, and a range of indicators on how public money is spent.
Dublin may not yet be best in class, but it's getting there.