In 2368, the Krocton Segment was represented by Senator Pardek. Pardek maintained a dwelling in Krocton; he visited on the third day of the Romulan week when the Romulan Senate was not in session. He also had family in the area, including one that was a legal intercessor.
That year, Federation Captain Jean-Luc Picard and Lieutenant Commander Data visited the Krocton Segment as part of their undercover attempt at making contact with Ambassador Spock. They first observed the interecessor's office belonging to a relative of Pardek from a nearby restaurant. Later, Picard and Data were apprehended by the Romulan underground movement, who took them to meet Spock in a nearby caves. (TNG: "Unification I", "Unification II")
In the script for "Unification I", the establishing matte painting was described as an exterior view of the "Capitol city" of Romulus in daylight. This Capitol city is also where the sets (the street, the caves, and the office) were supposed to be located.
A "segment" is a region of a circle which is cut off from the rest by a chord. As the city shown on the matte painting appears to be circular, "Krocton Segment" might only refer to a part of it.
The novelization of "Unification" describes the Romulan police going back to the Krocton Segment and killing many of the residents as a result of the failure of Sela and Pardek's plan. The Krocton Segment is described as a portion of the Romuluan capitol of Ki Baratan (β) or Dartha in other novels including Beneath the Raptor's Wing, and it's mirror universe counterpart is mentioned in The Sorrows of Empire.