This unique, partly ruined mud-brick structure has 18 extraordinarily sturdy rear columns that date from about AD 760 – reputedly making this the second-oldest mosque in Iran (though it may have started life as a Zoroastrian palace-temple). The broken columns and partly renovated arches of a colonnaded courtyard are similarly massive and undecorated. In striking contrast, the 30m-high brick minaret (from 1038) is very finely detailed. Now slightly leaning, it’s within the yard of a new mosque next door.
On Saturdays entry is by arrangement only.