Darıca

Antonius then moved on to the Ottoman holdings in Darıca, nothing special about this place with no natural bay making it a safe harbour from the not so dangerous Mediterranean tides, no strong fortress built here stopping the aggressors at its door steps, no tough terrain making it unreachable, and definitely no strong opposition army here to fend off its invaders, if one wants to set up a sea side outpost or fortress here to spy and blockade the ships sailing into the strait, this place is not the best option, so what makes it so damn important that Sultan Orhan must specifically include it in the deal requesting Antonius to take it? 

Because it is rich.