A conference hall or conference room is a room provided for singular events such as business conferences and meetings. It is commonly found at large hotels and convention centers though many other establishments, including even hospitals, have one. Sometimes other rooms are modified for large conferences such as arenas or concert halls. Aircraft have been fitted out with conference rooms. Conference rooms can be windowless for security purposes. An example of one such room is in the Pentagon, known as the Tank. Typically, the facility provides furniture, overhead projectors, stage lighting, and a sound system. Smoking is normally prohibited in conference halls even when other parts of buildings permit smoking. Sometimes the term 'conference hall' is used synonymously with 'conference center' as, for example, in 'Bandaranaike Memorial International Conference Hall'