How we can create network for 5 cities by using routers & switches?

there is many ways to establish this WAN , Site-to site VPN through internet is most easiest and cheapest one., other ways depend on ISP telecoms to provide either transmission fiber or more advanced L2,L3 connectivity , L2 & L3 is preferable as it offer high redundancy through ISP core MPLS routers. one more one is used nowadays is LTE as backup link for primary fiber link ...

Depending on the available resources and capital, use of Virtual Private Network (VPN) is employed to connect  these cities over Wide Area Network (WAN). Routers are then used to connect network and forward packets to different cities or destinations. Recall, router is a layer 3 device that forwards packets based on the information in the layer 3 IP packets (destination IP address). Further, switches are used to channel incoming data from input ports to the specific output port that leads the information to the intended cities.

Depending on the budget and requirements. For example we can choose to implement MPLS between all the cites and switches for the internal networks. Or we can use VPN technology to connect all the cites over WAN and switches behind the edge routers for the internal networks

.with internet, use router and WAN protocols 

without internet, contact STC ask for IPVPN using their infrastructure for secure connection