A couple of hundreds of meters from the Kilitbahir fortress (and seemingly connected to it at some time) there is a series of what I, as a layman, call bunkers - or maybe the word casemate is more proper. Very impressive and extensive, some in several floors. Must have been hell to live there, but now they are serene. They seem to date from the 1890's.
The museum inside has been much improved, with light- and sound effects to give some feel of what it was like during offensives and lots of explanations for the historically inclined.