Jameh Mosque of Semnan or Semnan Central Mosque was constructed in the 1st century AH. on the site of the ruins of an ancient fire-temple. Evidences can be noted here from the Mongol and Teimoorid periods. Its tall brick made porch on the western side of the courtyard, was constructed under the orders of a minister Khajeh Shamseddin Balijeh Semnani and the dome by Khajeh Abu Saeid, the former during the reign of Soltan Shahrokh Teimoori and the latter in the times of Soltan Sanjar. There is an inscription on the upper portion of the porch, under which are a few huge tablets of stone. Two of which are decrees of the Safavid monarch to the public.