A velodrome is an arena for track cycling. Modern velodromes feature steeply banked oval tracks, consisting of two 180-degree circular bends connected by two straights. The straights transition to the circular turn through a moderate easement curve. History The first velodromes were constructed during the late 1870s, the oldest of which is Preston Park Velodrome, Brighton, United Kingdom, built in 1877 by the British Army. Some were purpose-built just for cycling, and others were built as part of facilities for other sports; many were built around athletics tracks or other grounds and any banking was shallow. Reflecting the then-lack of international standards, sizes varied and not all were built as ovals: for example, Preston Park is long and features four straights linked by banked curves, while the Portsmouth velodrome, in Portsmouth, has a single straight linked by one long curve. Early surfaces included cinders or shale, though concrete, asphalt and tarmac later became more common. Indoor velodromes were also common particularly in the late 19th and early 20th century. For example, the Vélodrome d'hiver was built in Paris in 1909 and featured a indoor track with a wooden surface. International competitions such as the Olympic Games led to more standardisation: two-straight oval tracks quickly became the norm, and gradually lap lengths reduced. The Vélodrome de Vincennes, used for the 1896 (and 1924) Games was per lap, while Antwerp's Vélodrome d'Anvers Zuremborg, used in 1920, and Helsinki Velodrome, used in 1952, were both . By the 1960s up to 1989, tracks of length were commonly used for international competitions (e.g.: the Agustín Melgar Olympic Velodrome used for track cycling events at the 1968 Summer Olympics, and Leicester's Saffron Lane velodrome used at the 1970 and 1982 Track Cycling World Championships). Since 1990, such events are usually held on velodromes with laps. London's 2012 Olympic velodrome and a new velodrome in Turkmenistan's capital city Ashgabat both have a 250 m track and a 6,000-seat spectator capacity. Technical aspects Banking in the turns, called cant, allows riders to keep their bikes relatively perpendicular to the surface while riding at speed. When travelling through the turns at racing speed, which may exceed , the banking attempts to match the natural lean of a bicycle moving through that curve. At the ideal speed, the net force of the centrifugal force (outward) and gravity (downward) is angled down through the bicycle, perpendicular to the riding surface.