An '''oculus''' is a circular opening in a roof which allows for rain and sunlight to spill through the roof to illuminate the interior of a building.<ref>''Oculus'' [http://cancerweb.ncl.ac.uk/cgi-bin/omd?oculus Websters Dictionary]. Accessed 12 January 2008.</ref> [[Vatican]] architecture, especially in [[Saint Peter's Basilica]], makes great use of this architectural device. It is a relic of Roman times, in a way, and was used in circular, vaulted temples like the [[Pantheon]] under the Republic.
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An '''oculus''' is a circular opening in a roof which allows for rain and sunlight to spill through the roof of a building.<ref>''Oculus'' [http://cancerweb.ncl.ac.uk/cgi-bin/omd?oculus Websters Dictionary]. Accessed 12 January 2008.</ref> [[Vatican]] architecture, especially in [[Saint Peter's Basilica]], makes great use of this architectural device. It is a relic of Roman times, in a way, and was used in circular, vaulted temples like the [[Pantheon]] under the Republic.