In other news, Hap's got it right, but you can also travel to Firewatch via Effe-Tei (Mournhold transportation bloke).
Correct, so here's the complete list of all ways to reach Map 1 until third-part mods are released:
1) Divine Intervention from Tel Mora > Firewatch, just outside Imperial Cult chapel
2) ALMSIVI intervention from Sadrith Mora > Ranyon-ruhn, just outside Temple
3) Argonian bloke (Effe-Tei) in Mournhold > Firewatch
4) Levitation, swimming, waterwalk
5) "Icarian Fly"
Thanks for the infos! So the new Bal Oyra vendors are in the exteriors?
Agreed. My favourite is the scrib pie.