If an organization in a city (perhaps New York) has multiple offices within that city, how would they interconnect their LANs? I already understand that they will connect to an ISP, but my question is: Does a MAN travel across the internet to connect their networks where they have routers running eBGP?
There are quite a few possibilites.
They can get a dark fiber from an ISP and interconnect their network equipment, in this case they "own" the whole network and they are fully responsible for routing between different offices.
They also can get plain Internet access in each location and build a secure overlay network, like DMVPN. The branch offices of course can run BGP with ISPs.
Another option is to get some sort of L2/L3 VPN from an ISP. In case of L2VPN the offices will be directly connected in L2. In case of L3 VPN, the company's equipment usually will have to run some sort of routing protocol with ISP, who will "own" company's core network.
Metropolitan Area Networks (MAN) connectivity is wide range of connectivity act between LAN and WAN networks
To connect multiple offices of same organization within city , there are possible options
Can connect with point to point lease lines and Configure static routing among this site's between two offices
Built IPsec Site to Site VPN tunnels between two offices and Configure routing on tunnel to pass interesting traffic among tunnel .
From techopedia - It does establish it connection through an ISP so it travels the internet
Metropolitan Area Network (MAN) Definition - What does Metropolitan Area Network (MAN) mean? A metropolitan area network (MAN) is similar to a local area network (LAN) but spans an entire city or campus. MANs are formed by connecting multiple LANs. Thus, MANs are larger than LANs but smaller than wide area networks (WAN).
MANs are extremely efficient and provide fast communication via high-speed carriers, such as fiber optic cables.