The last remaining of five bathhouses in Gaza City, Hammam al-Samara is a gorgeous Mamluk-era bathhouse dating back even beyond the 14th century, when, according to a plaque in the lobby, it was restored by the governor Sangar ibn Abdullah. It has managed to retain its vaulted ceilings and inlaid marble tiled floors, and is still heated by a series of wood-fired ovens and aqueducts.
Because of ongoing restoration work, opening times may change, but if open, it's a great place for a leisurely steam-clean with the locals.