Rio de Janeiro, commonly known as Rio, is the capital of the state of Rio de Janeiro and the second-largest city in Brazil. It is a key city in the country, playing an important role in Brazil's history, economy, and culture. Founded in 1565 by the Portuguese, Rio de Janeiro initially served as the seat of the Captaincy of Rio de Janeiro, which was part of the Portuguese Empire.

In 1763, the city became the capital of the State of Brazil, a province under Portuguese rule. When the Portuguese Royal Court moved to Brazil in 1808 to escape Napoleon’s invasion, Rio de Janeiro became the royal court's seat. In 1815, under Prince Regent João VI, Brazil was elevated to the status of a kingdom, forming the United Kingdom of Portugal, Brazil, and the Algarves. Rio de Janeiro remained the capital of this pluricontinental monarchy until 1822, when Brazil's war for independence began. This makes Rio one of the rare instances where a colonial capital became the seat of the ruling empire.

After Brazil gained independence, Rio continued as the capital of the Empire of Brazil until 1889. When Brazil transitioned from a monarchy to a republic, Rio de Janeiro remained the capital until 1960, when the capital was moved to Brasília.

Rio de Janeiro is known for its unique geography and landmarks, including the world-famous Christ the Redeemer statue on Corcovado Mountain, which is one of the New Seven Wonders of the World. The city is a major tourist destination in the Southern Hemisphere, attracting millions of visitors annually with its beaches, cultural events, and natural beauty. In 2016, Rio became the first South American city to host the Summer Olympics, further highlighting its global significance.

In addition to its cultural heritage, Rio de Janeiro is a key economic center in Brazil, home to major companies in industries such as oil, mining, and telecommunications. Its historic and economic importance, along with its global appeal, makes Rio one of the most prominent cities in Latin America.
 

• The city proper has a population density of 5,377 people per square kilometre (13,930 per square mile).
• The city proper covers a total surface area of 1,221 km² (486.5 sq mi), while the metropolitan region expands to 4,539.8 km² (1,759.6 sq mi).
• Rio’s carnival is the largest in the world. According to the Guinness Book of Records, in 2004, the city’s renowned celebration attracted a record 400,000 foreign visitors, making it the biggest carnival globally. Every year, around 5 million people participate in the city’s street parties, called “blocos,” organised by samba groups.
• Rio is home to the eighth-largest library in the orld: the National Library of Brazil.
• The city houses the largest urban forest in the world, the Tijuca National Park.
• People from Rio are among the quickest when it comes to boarding and alighting buses. Buses are the most affordable way to travel in the city, but riding them can be challenging due to fast-paced drivers who may leave passengers behind if they are not quick enough to board.
• The statue of Christ the Redeemer was voted as one of the New Seven Wonders of the World.
• Rio de Janeiro hosted the 2016 Summer Olympics, becoming the first South American city to host the event.
• The Maracanã Stadium, located in Rio, is one of the world’s largest football stadiums, with a seating capacity of over 78,000.
   

The city of Rio de Janeiro is divided into five principal Planning Zones (APs) and 30 Administrative Districts (RAs). These divisions help manage the city's governance and urban planning.

The Municipal Chamber of Rio de Janeiro serves as the unicameral legislative body of the city, responsible for passing laws and overseeing municipal governance. It was established in 1565 by the Portuguese colonists, making it one of the oldest governing institutions in the city. The chamber plays a vital role in shaping policies related to public services, infrastructure, and urban development.

Rio de Janeiro has a diverse and strong economy, providing significant employment in sectors such as heavy and light industry, manufacturing, commerce, finance, trade, and other services. As the capital of Brazil for many years, Rio attracted considerable investment from profitable companies, positioning it as an important economic hub. Until the late 19th century, Rio was the richest state in Brazil before São Paulo overtook it.

Agriculture remains a part of Rio’s economy, with large-scale investment in sugarcane production, especially in the Campos region. Orange cultivation is another key aspect of the farming sector. While coffee was once a major industry, its significance has diminished due to environmental factors. Other food grains are produced but not in large quantities for export. Livestock farming also plays a role, and fishing, particularly for sardines, is a significant part of the economy.

Rio’s economy has benefited from oil exploration in the nearby Campos Basin. International oil companies such as Shell, EBX, and Esso have established a presence in the city. Several large companies, particularly in the telecommunications sector, have their headquarters in Rio, including Oi and Embratel. Rio is Brazil's second-largest industrial hub and a major financial and service centre. The financial sector, especially banking, plays a crucial role in the city’s economy. Rio’s stock exchange, Bolsa de Valores, is the second most active stock market in Brazil.

Tourism is another vital contributor to Rio’s economy. The city attracts both international and domestic visitors due to its world-famous carnival, beaches, and natural beauty. The diversity of cultures, traditions, and cuisine draws tourists, and the city’s tropical climate allows for year-round visits. Additionally, Rio de Janeiro hosted major global events like the 2016 Summer Olympics, further boosting tourism and infrastructure development.

New developments in sectors like tech, media, and entertainment are also contributing to Rio’s economy. The city's growing media and television production industry, centred around Estúdios Globo, has become a key player in the Brazilian entertainment sector.
 

In recent years, Rio de Janeiro has made significant investments in public transportation to improve mobility across the city. One of the key developments was the introduction of the Bus Rapid Transit (BRT) system. In 2014, the city received the Sustainable Transport Award for its Transcarioca BRT corridor. This route connects 27 neighbourhoods and stretches over 39 kilometres, featuring 47 stations. The Transcarioca system integrates with other forms of public transportation, including metropolitan rail, subways, and Rio’s first BRT system, TransOeste. It notably connects with the International Airport in Guanabara Bay, making travel to and from the airport much easier for residents and visitors alike.

Ahead of the 2016 Olympic Games, Rio underwent a construction boom to accommodate the event, leading to new sports venues, improved public spaces, and upgraded infrastructure. One of the major projects was the extension of the subway system, designed to link key areas like the popular beach zones with the Olympic Park. Although the full opening of the extension faced delays, the line was completed in time to serve athletes and spectators during the Games. This subway extension has since become a vital link for residents, easing congestion in previously underserved areas.

Rio also made advancements in its light rail system, integrating modern trams into the city’s public transport network. The light rail now connects the downtown area to the port and surrounding neighbourhoods, improving accessibility and reducing reliance on cars.

Despite these improvements, Rio continues to face challenges related to urban mobility and traffic congestion. Efforts are ongoing to enhance the quality of transportation services and expand access to different parts of the city, especially in the face of growing population demands and environmental concerns. Plans for further extensions of the BRT and metro systems are being discussed as part of Rio’s broader strategy to promote sustainable urban development by 2024.

Rio de Janeiro has embraced advanced technology to manage its city services efficiently. One of the key initiatives is the use of IBM's Smart Cities technology, which allows the city to coordinate services in real-time. From responding to emergencies to managing traffic flow, the system provides an integrated platform to enhance urban operations. The city's Operations Centre, established with IBM's expertise, is the only one of its kind and acts as a central hub for monitoring and controlling various city services. The idea behind this system is to create a model that, if it works in a large city like Rio—especially during busy periods like Carnaval—can be adapted to other cities worldwide. IBM has reported that it is now scaling this technology for smaller and medium-sized cities, demonstrating the system's versatility.

Additionally, the city has made strides in sustainable development through the Rio de Janeiro Low Carbon City Development Program (LCCDP). This programme, launched in 2012 at the Rio+20 Conference, provides a structured framework for the city to plan, implement, and monitor low-carbon investments and climate change mitigation actions. The programme is certified by the International Organization for Standardization (ISO) and serves as a model for other cities looking to implement low-carbon strategies. By achieving these international standards, Rio has positioned itself as a global leader in sustainable urban development.

In 2024, Rio continues to integrate technology into various sectors to improve urban life. Initiatives such as enhanced data analytics for public transport, expanded monitoring of environmental conditions, and new smart lighting systems are all part of the city's ongoing efforts to modernise and become more efficient. These efforts not only improve the quality of life for residents but also help reduce the city's environmental impact.

Future plans include expanding the Smart Cities model further into public safety, education, and healthcare systems, ensuring that Rio continues to leverage technology for smarter and more sustainable city management.