With a land area of 1,420 km², it is more compact than Sub-cluster 1-2 but has a higher proportion of urban areas (75.4%).
Ceir arwynebedd tir o 1,420 km², ac felly mae’n llai nag is-glwstwr 1-2 ond mae’n cynnwys cyfran uwch o ardaloedd trefol (75.4%).