This is one of the three first buildings in the baroque style. It is a sebil, built in 1741-42, for cavalry captain Hacı Mehmed Emin Agha, that is connected to a small graveyard, built at the same time. The grave of the captain is within the sebil (most unusual). Of the three this is the most impressive one, with columned capitals, and calligraphy in the old style, the latter contrasting with the new style visible in the rest. Source: Ünver Rüstem: Ottoman Baroque.
The door opened to the small cemetery.