The roof is curved. It may be of a regular round arched shape, or more irregularly curved when viewed in section.

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Curved roof, Rogers Arena, Vancouver, Canada (S. Brzev)

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Curved roof (earthen dome), Iran (F. Naeim, World Housing Encyclopedia Report 104)

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Irregular curved roof, Canada (S. Brzev)

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Regular curved roof, Canada (S. Brzev)

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Curved roof shape, Beijing Capital International Airport, China (S. Brzev)