Here, on Patan's Durbar Square, stands the valley's greatest concentration of major temples and historic buildings.
Here, on Patan's Durbar Square, stands the valley's greatest concentration of factories and smelters. 
mnli hypothesis: Here, on Patan's Durbar Square, stands the valley's greatest concentration of factories and smelters.  premise: Here, on Patan's Durbar Square, stands the valley's greatest concentration of major temples and historic buildings.