The Mihrimah Sultan Mosque, is an Ottoman mosque, is quite close to the city walls and the Edirne Gate. It is located Edirnekapı section in Fatih district of Istanbul. The mosque was built by the architect Mimar Sinan for the daughter of Sultan Süleyman the Magnificent, Mihrimah Sultan. There are several buildings in various districts of İstanbul devoted to her. In Üsküdar has same name mosque was built by the architect Mimar Sinan for her.
Google Maps - Mihrimah Sultan Mosque

Mihrimah Sultan is daugther of Sultan Suleyman the Magnificent and his wife Hurrem Sultan. The Mihrimah Sultan complex was built by the architect Mimar Sinan in 1562-1565.
There is a myth about these two Mosques. It is said that Mimar Sinan fell in love with Mihrimah and built the smaller mosque in Edirnekapı without palace approval, on his own, dedicated to his love. The legend continues to say that on 21st of March (when day time and night time are equal and Mihrimah's alleged birthday, hence the name) at the time of sunset, if you have clear view of both mosques, you will notice that as the sun sets behind the only minaret of the mosque in Edirnekapı, the moon rises between the two minarets of the mosque in Üsküdar.

The Mihrimah Sultan Mosque is quite closed to Edirnekapı. You can go to Edirnekapı by metrobus, T4 Edirnekapı-Sultançiftliği tram or Public buses.
Public Bus - Edirnekapı