The Petronas Towers, also known as the Petronas Twin Towers are twin skyscrapers in Kuala Lumpur, Malaysia. According to the CTBUH's official definition and ranking, they were the tallest buildings in the world from 1998 to 2004 until surpassed by Taipei 101, but they remain the tallest twin buildings in the world.The buildings are the landmark of Kuala Lumpur with nearby Kuala Lumpur Tower.The towers were designed by Argentine architect César Pelli. They chose a distinctive postmodern style to create a 21st-century icon for Kuala Lumpur. Planning on the Petronas Towers started on 1 January 1992 and included rigorous tests and simulations of wind and structural loads on the design. Seven years of construction followed, beginning on 1 March 1993 with the excavation, which involved moving 500 truckloads of earth every night to dig down 30 metres below the surface.The construction of the superstructure commenced on 1 April 1994. Interiors with furniture were completed on 1 January 1996, the spires of Tower 1 and Tower 2 were completed on 1 March 1996, and the first batch of 'PETRONAS’ personnel moved into the building on 1 January 1997. The building was officially opened by the Prime Minister of Malaysia's Tun Dr. Mahathir bin Mohamad on 1 August 1999.The twin towers were built on the site of Kuala Lumpur's race track.Test boreholes found that the original construction site effectively sat on the edge of a cliff. One half of the site was decayed limestone while the other half was soft rock. The entire site was moved 61 metres to allow the buildings to sit entirely on the soft rock. Because of the depth of the bedrock, the buildings were built on the world's deepest foundations.104 concrete piles, ranging from 60 to 114 metres deep, were bored into the ground. The concrete raft foundation, comprising 13,200 cubic metres of concrete was continuously poured through a period of 54 hours for each tower. The raft is 4.6 metres thick, weighs 32,500 tonnes and held the world record for the largest concrete pour until 2007.The foundations were completed within 12 months by Bachy Soletanche and required massive amounts of concrete.Its engineering designs on structural framework were contributed by Haitian engineer Domo Obiasse and colleagues Aris Battista and Princess D Battista.The 88-floor towers are constructed largely of reinforced concrete, with a steel and glass facade designed to resemble motifs found in Islamic art, a reflection of Malaysia's Muslim religion.Another Islamic influence on the design is that the cross section of the towers is based on a Rub el Hizb, albeit with circular sectors added to meet office space requirements.As a result of the Malaysian government specifying that the buildings be completed in six years, two construction consortiums were hired in order to meet the deadline, one for each tower. Tower 1, the west tower was built by a Japanese consortium led by the Hazama Corporation while Tower 2, the east tower was built by a South Korean consortium led by the Samsung C&T Corporation. Early into construction a batch of concrete failed a routine strength test causing construction to come to a complete halt. All the completed floors were tested but it was found that only one had used a bad batch and it was demolished. As a result of the concrete failure, each new batch would now be tested before being poured. The halt in construction had cost US$700,000 per day and led to three separate concrete plants being set up on the site to ensure that if one produced a bad batch, the other two could continue to supply concrete. The sky bridge contract was completed by Kukdong Engineering & Construction. Tower 2 became the first to reach the world's tallest building at the time. But Tower 1 ran into problems when they discovered the structure was leaning 25 millimetres off from vertical. To correct the lean, the next 16 floors were slanted back 20 millimetres with specialist surveyors hired to check verticality twice a day until the building's completion.Due to the huge cost of importing steel, the towers were constructed on a cheaper radical design of super high-strength reinforced concrete.High-strength concrete is a material familiar to Asian contractors and twice as effective as steel in sway reduction; however, it makes the building twice as heavy on its foundation than a comparable steel building. Supported by 23-by-23 metre concrete cores and an outer ring of widely spaced super columns, the towers use a sophisticated structural system that accommodates its slender profile and provides 560,000 square metres of column-free office space.Below the twin towers is Suria KLCC, a shopping mall, and Dewan Filharmonik Petronas, the home of the Malaysian Philharmonic Orchestra.