Citation Captain reported while being vectored to an ILS approach accepting a visual approach and misidentified the airport resulting in turning base for the wrong airport and flying towards terrain.

Narrative

We briefed the training traffic at ZZZ as a threat prior to departure from ZZZ1. As we were completing the ZZZZZ arrival into a planned ILS XXR approach; ZZZZZ approach asked if we wanted the visual approach instead. I misidentified ZZZ2 as ZZZ; called the field in sight and began a right turn to enter a downwind leg for XXR. After turning base and beginning a visual descent over terrain we received a 'sink rate' aural alert and a yellow TERRAIN CAS message. We evaluated the situation and I reduced the rate of descent and then realized we were lined up for the wrong airport prior to turning on about a 6 mile final. We then correctly identified and verified ZZZ and proceeded towards a left base for XXR giving the traffic in the pattern for ZZZ XXL a wide berth. As we settled into the final for XXR; tower called traffic at our 10 o'clock level and converging for the parallel. Neither myself or my copilot saw the traffic for more than a moment; as it passed below our line of sight and behind us. TCAS was showing the traffic inside of 2 miles and less than 300 of separation. I initially added power to gain more altitude separation but since neither of us could see the traffic my copilot correctly called for a go-around. We entered a right traffic pattern at 2000 and got extended enough on the downwind for traffic that we had to climb due to terrain. Tower called our base turn and an uneventful landing ensued. Suggestions: Lesson learned here; was to more carefully consider the choice to accept the visual approach especially with traffic and terrain considerations even when weather is clear. It's likely that a normal ILS Z XXR would have made for a far more uneventful approach.