The Alaca İmaret mosque is located in the north part of the center of Thessaloniki, northeast of the church of Agios Dimitrios, within the city block that is bounded by the streets Cassander, Sophocleous, Galileou and Agiou Nikolaou. This is a remarkable Ottoman building, which operated - except as a muslim mosque – as an imaret (poors’ house) and a Medrese (ieratical school). According to a dedicatory inscription that survives above the entrance of the building, its construction was made in 1484 by İshak Paşa, who was the Grand Vizier and Governor of the city. For this reason, the monument is also known with the name «İshak Paşa Mosque." Today, the area belongs to the municipality of Thessaloniki and is used for cultural events and temporary exhibitions.
The Alaca İmaret mosque has the shape of an inverted T and comprises of a rectangular main prayer hall, which is covered by two large domes, four lateral appartments, covered also with domes, which served the rations and the holy teaching, and a pillar-based arcade in front, which has on its roof five small domes. All domes were originally covered with lead sheets. In the southwestern corner of the building there was a minaret, which was demolished between 1925 and 1930, as it happened with other minarets of Thessaloniki, thus surviving mowadays only its base. The face of the minaret was decorated with colorful stones forming lozenges, element rarely found in Ottoman architecture. It was the most impressive building of its kind in town, as it turns out both from old photographs and the enthusiastic descriptions of travelers. The monument was internally decorated with murals, which depicted simple floral patterns and inscriptions with quotes from the Koran.