St Mark's church was located on the north-east side of Park Terrace at its junction with Lion Street. It was built 1887 to a minimal design by Habershon & Fawckner, constructed of coursed rubble under tiled roofs and consisting of nave and chancel, lean-to porch and gabled (?) vestry.
It appears to have been demolished (in about 1990) and replaced by a housing development.
Sources:
J.Newman, Buildings of Wales: Glamorgan (1995), p.610.
http://www.churches-uk-ireland.org/images/swansea/swansea/mark.jpg (image).

David Leighton, RCAHMW, 19 May 2015