ators , ▁also ▁called ▁metropol itan ▁functions : ▁The ▁decision ▁making ▁and ▁control ▁function , ▁the ▁innov ation ▁and ▁competition ▁function , ▁and ▁the ▁gateway ▁function . ▁These ▁functions ▁are ▁seen ▁as ▁key ▁domains ▁for ▁metropol itan ▁regions ▁in ▁developing ▁their ▁performance . ▁ ▁In ▁spatial ▁planning , ▁a ▁metropol is ▁is ▁usually ▁observed ▁within ▁its ▁regional ▁context , ▁thus ▁the ▁focus ▁is ▁mainly ▁set ▁on ▁the ▁metropol itan ▁regions . ▁These ▁regions ▁can ▁be ▁mon o ▁central ▁or ▁multi ▁central . ▁Ele ven ▁metropol itan ▁regions ▁have ▁been ▁defined ▁due ▁to ▁these ▁indic ators : ▁Berlin - Br andenburg , ▁Bre men - Old enburg , ▁Dresden - H alle - Le ip zig , ▁Frankfurt - R h ine - Main , ▁Hamburg , ▁Hannover - Bra un sch weig - G ött ingen - W olf s burg , ▁Mun ich , ▁N ure m berg , ▁Rh ine - Ne ck ar , ▁Rh ine - R u hr ▁( with ▁C ologne / B onn ), ▁and ▁Stuttgart . ▁ ▁Hung ary ▁ ▁Budapest ▁has ▁a ▁population ▁of ▁ 1 ▁ 7 5 0 ▁ 0 0 0 , ▁more ▁than ▁eight ▁times ▁the ▁population ▁of ▁the ▁second ▁largest ▁city , ▁Deb rec en . ▁ ▁Italy ▁▁ ▁As ▁of ▁January ▁ 1 , ▁ 2 0 1 5 , ▁there ▁are ▁ 1 4 ▁" met ropol itan ▁cities " ▁in ▁Italy . ▁Rome , ▁Milan , ▁Nap les ▁and ▁other ▁big ▁cores ▁have ▁taken ▁in ▁urban