The Gazi Ahmet Paşa Mosque is not far from the Topkapı stop of the tramway (one stop earlier, Pazartekke to be precise), and the city wall (NOT the Topkapı palace museum, which is at the other end of town).

This mosque is sometimes also named ‘Topkapı Camisi’ (because of its location).
It was commissioned by Kara Ahmet Paşa (‘Black Ahmet’), a Grand Vizir (and brother-in-law) of Süleyman the Magnificent. He was married to Fatma Sultan, a daughter of Süleyman’s father Selim I.
The building works started in 1555 (shortly before Ahmet Paşa died), and finished three years later under supervision of Rüstem Paşa, another Grand Vizier (and a son-in-law) of sultan Süleyman.
The courtyard north of the mosque has a large şadırvan (fountain for ritual ablutions) in its center; it is surrounded by a medrese, with cells for the students and a dershane (main classroom). The türbe (mausoleum) of Kara Ahmet Paşa (built 1558) stands next to the mosque.

Correspondent: J.M.Criel, Antwerpen.
Sources: ‘Türkiye Tarihi Yerler Kılavuzu’ – M.Orhan Bayrak, Inkılâp Kitabevi, Istanbul, 1994
& Vikipedia.