nostr:npub1dc07dfupqmgagu9r4p3ndyv47q6zmnfqguneqmra6jvuadwpxdpqe6aqev nostr:npub16mnm47tsg3yurkqacgunnhmj7thmzeck8r0r3aphwxqqlpf24ges2uf35z
As a working example of this, take the VOICE room that started as;
#VOICEChat:matrix.org
It's now also accessible as;
#VOICEChat:matrix.iridescent.nz
Other room members can create local addresses on the homeserver they use, and these too can be published as ways of addressing the same room.
Room history is a bit more complicated. But every homeserver has a history from the time a person using it joined, and complete histories can be synced using the protocol.