Houston has the third tallest skyline in North America and one of the top 10 in the world. A seven-mile (11 km) system of tunnels and skywalks link downtown buildings containing shops and restaurants, enabling pedestrians to avoid summer heat and rain while walking between buildings.
In the 1960s, Downtown Houston consisted of a collection of mid-rise office structures. Downtown was on the threshold of an energy industry led boom in 1970. A succession of skyscrapers were built throughout the 1970s—many by real estate developer Gerald D. Hines—culminating with Houston's tallest skyscraper, the 75-floor, 1,002-foot (305 m)-tall JPMorgan Chase Tower (formerly the Texas Commerce Tower), completed in 1982. It is the tallest structure in Texas, 10th tallest building in the United States and the 30th tallest skyscraper in the world, based on height to roof. In 1983, the 71-floor, 992-foot (302 m)-tall Wells Fargo Plaza (formerly Allied Bank Plaza) was completed, becoming the second-tallest building in Houston and Texas. Based on height to roof, it is the 13th tallest in the United States and the 36th tallest in the world. As of 2007, downtown Houston had over 43 million square feet (4,000,000 m²) of office space.
Centered on Post Oak Boulevard and Westheimer Road, the Uptown District boomed during the 1970s and early 1980s when a collection of mid-rise office buildings, hotels, and retail developments appeared along Interstate 610 west. Uptown became one of the most prominent instances of an edge city. The tallest building in Uptown is the 64-floor, 901-foot (275 m)-tall, Philip Johnson and John Burgee designed landmark Williams Tower (known as the Transco Tower until 1999). At the time of construction, it was believed to the be the world's tallest skyscraper outside of a central business district. The Uptown District is also home to buildings designed by noted architects I. M. Pei, César Pelli, and Philip Johnson. In the late 1990s and early 2000s decade, there was a mini-boom of mid-rise and high-rise residential tower construction, with several over 30 stories tall. In 2002, Uptown had more than 23 million square feet (2,100,000 m²) of office space with 16 million square feet (1,500,000 m²) of Class A office space.