Alacamescit Mosque, one of the oldest cultural heritages of Izmit, near the Saatçi Ali Efendi Mansion in Veliahmet Neighborhood was built by Mustafa Bin Mehmet Bey Gumuşluzade (Gumuşluoğlu, Kadi of Izmit – Gumuşizade IV. Murat Period) in 1007 (Hijri), in 1598-1599 (Gregorian Calender). The Mosque was built according to square plan and has masonry walls. Narthex has wooden fringe. Minaret getting attention with its height in comparison to prayer room is masonry also. Under the minaret balcony is spiked harmoniously with the prayer room fringe. It was ruined in 1999 Marmara earthquake and rebuilt in accordance with the original building.
On a ceramic inscription with thuluth script in dark blue on white background of the Mosque, it is written:
Bena haza’l-mescide taleben li-rıza’l-lahi
Te’ala vebtigae li-rahmeti Rabbihi’l-ala
El-Hac Mustafa Bin Muhammed eş-şehir bi-Gumuşluzade
Tarih fi sene Seb’a ve elf h.1007(1598-1599)