Where does an ISP connect to?

I was wondering, they say that the Internet is a group of networks, and I connect to my ISP so they can connect me to the Internet, but where exactly does my ISP connect to? to another network (which connects to another network)? if so, why can't I connect to that network , instead of having to pay an ISP to connect me to them?

Thanks

ISP's connect to backbones and international links. You cant connect to them because you dont have the required hardware / software as well as the money

Basically everything is a collection of networks.. think about it.. your small home LAN is a little network, it connects to an ISP, where it becomes part of the ISP's larger network, your ISP connects to other ISP's, which in turn become one huge network.

Thats why the Internet would be very difficult to shut down even in the event of a nuclear war... because if even two machines remain standing, the Internet is still alive.

Also to add…in the beginning there used to be about a half a dozen primary backbone providers i.e.: UU.net, ELI, AT&T and MCI, now there are a lot more, check out the links provided.

www.webopedia.com/TERM/U/UUNET.html
www.mci.com/index.jsp
www.isp-planet.com/resources/backbones/


Best Regards,