The town's Friday mosque is the highlight of a visit to Na'in. Constructed between the 10th and 11th centuries, it was one of the first mosques built in Iran and is unusual in that it doesn't conform to the usual four-iwan plan of its time (eg the Masjed-e Jameh in Esfahan). The exterior facade and minaret are austerely beautiful and many parts of the interior (including the mihrab) are decorated with finely detailed stucco work.
The courtyard is decorated with 14 columns, each of which displays a different brickwork pattern. Further interesting features include the exquisitely carved wooden minbar, which an inscription identifies as being 700 years old, and an underground prayer hall, designed to keep the faithful cool in summer and warm in winter. Alabaster 'windows' set in the ceiling of this dug-out basement allowed natural light to filter down from the courtyard, and access to the qanat below the mosque served as the ablutions area.