diff --git a/src/domain/session/RoomViewModelObservable.js b/src/domain/session/RoomViewModelObservable.js
index 9252ee81..b9549905 100644
--- a/src/domain/session/RoomViewModelObservable.js
+++ b/src/domain/session/RoomViewModelObservable.js
@@ -36,6 +36,7 @@ This is also why there is an explicit initialize method, see comment there.
 export class RoomViewModelObservable extends ObservableValue {
     constructor(sessionViewModel, roomId) {
         super(null);
+        this._statusSubscription = null;
         this._sessionViewModel = sessionViewModel;
         this.id = roomId;
     }
@@ -48,9 +49,9 @@ export class RoomViewModelObservable extends ObservableValue {
     */
     async initialize() {
         const {session} = this._sessionViewModel._sessionContainer;
-        this._statusObservable = await session.observeRoomStatus(this.id);
-        this.set(await this._statusToViewModel(this._statusObservable.get()));
-        this._statusObservable.subscribe(async status => {
+        const statusObservable = await session.observeRoomStatus(this.id);
+        this.set(await this._statusToViewModel(statusObservable.get()));
+        this._statusSubscription = statusObservable.subscribe(async status => {
             // first dispose existing VM, if any
             this.get()?.dispose();
             this.set(await this._statusToViewModel(status));
@@ -64,8 +65,9 @@ export class RoomViewModelObservable extends ObservableValue {
             return this._sessionViewModel._createRoomViewModel(this.id);
         } else if (status.archived) {
             return await this._sessionViewModel._createArchivedRoomViewModel(this.id);
+        } else {
+            return this._sessionViewModel._createUnknownRoomViewModel(this.id);
         }
-        return null;
     }
 
     dispose() {
diff --git a/src/domain/session/SessionViewModel.js b/src/domain/session/SessionViewModel.js
index ae697c72..6f2c9797 100644
--- a/src/domain/session/SessionViewModel.js
+++ b/src/domain/session/SessionViewModel.js
@@ -17,6 +17,7 @@ limitations under the License.
 
 import {LeftPanelViewModel} from "./leftpanel/LeftPanelViewModel.js";
 import {RoomViewModel} from "./room/RoomViewModel.js";
+import {UnknownRoomViewModel} from "./room/UnknownRoomViewModel.js";
 import {InviteViewModel} from "./room/InviteViewModel.js";
 import {LightboxViewModel} from "./room/LightboxViewModel.js";
 import {SessionStatusViewModel} from "./SessionStatusViewModel.js";
@@ -162,6 +163,13 @@ export class SessionViewModel extends ViewModel {
         return null;
     }
 
+    _createUnknownRoomViewModel(roomIdOrAlias) {
+        return new UnknownRoomViewModel(this.childOptions({
+            roomIdOrAlias,
+            session: this._sessionContainer.session,
+        }));
+    }
+
     async _createArchivedRoomViewModel(roomId) {
         const room = await this._sessionContainer.session.loadArchivedRoom(roomId);
         if (room) {
diff --git a/src/domain/session/room/RoomViewModel.js b/src/domain/session/room/RoomViewModel.js
index 1d2f3725..5d08f903 100644
--- a/src/domain/session/room/RoomViewModel.js
+++ b/src/domain/session/room/RoomViewModel.js
@@ -147,6 +147,14 @@ export class RoomViewModel extends ViewModel {
     forgetRoom() {
         this._room.forget();
     }
+
+    get canRejoin() {
+        return this._room.isArchived;
+    }
+
+    rejoinRoom() {
+        this._room.join();
+    }
     
     async _sendMessage(message) {
         if (!this._room.isArchived && message) {
diff --git a/src/domain/session/room/UnknownRoomViewModel.js b/src/domain/session/room/UnknownRoomViewModel.js
new file mode 100644
index 00000000..e7969298
--- /dev/null
+++ b/src/domain/session/room/UnknownRoomViewModel.js
@@ -0,0 +1,58 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {ViewModel} from "../../ViewModel.js";
+
+export class UnknownRoomViewModel extends ViewModel {
+    constructor(options) {
+        super(options);
+        const {roomIdOrAlias, session} = options;
+        this._session = session;
+        this.roomIdOrAlias = roomIdOrAlias;
+        this._error = null;
+        this._busy = false;
+    }
+
+    get error() {
+        return this._error?.message;
+    }
+
+    async join() {
+        this._busy = true;
+        this.emitChange("busy");
+        try {
+            const roomId = await this._session.joinRoom(this.roomIdOrAlias);
+            // navigate to roomId if we were at the alias
+            // so we're subscribed to the right room status
+            // and we'll switch to the room view model once
+            // the join is synced
+            this.navigation.push("room", roomId);
+            // keep busy on true while waiting for the join to sync
+        } catch (err) {
+            this._error = err;
+            this._busy = false;
+            this.emitChange("error");
+        }
+    }
+
+    get busy() {
+        return this._busy;
+    }
+
+    get kind() {
+        return "unknown";
+    }
+}
\ No newline at end of file
diff --git a/src/matrix/Session.js b/src/matrix/Session.js
index 38771c87..5a046117 100644
--- a/src/matrix/Session.js
+++ b/src/matrix/Session.js
@@ -717,6 +717,13 @@ export class Session {
             }
         });
     }
+
+    joinRoom(roomIdOrAlias, log = null) {
+        return this._platform.logger.wrapOrRun(log, "joinRoom", async log => {
+            const body = await this._hsApi.joinIdOrAlias(roomIdOrAlias, {log}).response();
+            return body.room_id;
+        });
+    }
 }
 
 export function tests() {
diff --git a/src/matrix/net/HomeServerApi.js b/src/matrix/net/HomeServerApi.js
index a3fe1bc9..f834b94b 100644
--- a/src/matrix/net/HomeServerApi.js
+++ b/src/matrix/net/HomeServerApi.js
@@ -190,6 +190,10 @@ export class HomeServerApi {
         return this._post(`/rooms/${encodeURIComponent(roomId)}/join`, null, null, options);
     }
 
+    joinIdOrAlias(roomIdOrAlias, options = null) {
+        return this._post(`/join/${encodeURIComponent(roomIdOrAlias)}`, null, null, options);
+    }
+
     leave(roomId, options = null) {
         return this._post(`/rooms/${encodeURIComponent(roomId)}/leave`, null, null, options);
     }
diff --git a/src/matrix/room/ArchivedRoom.js b/src/matrix/room/ArchivedRoom.js
index a87bd774..f975191e 100644
--- a/src/matrix/room/ArchivedRoom.js
+++ b/src/matrix/room/ArchivedRoom.js
@@ -162,6 +162,12 @@ export class ArchivedRoom extends BaseRoom {
             this._forgetCallback(this.id);
         });
     }
+
+    join(log = null) {
+        return this._platform.logger.wrapOrRun(log, "rejoin archived room", async log => {
+            await this._hsApi.join(this.id, {log}).response();
+        });
+    }
 }
 
 function findKickDetails(roomResponse, ownUserId) {
diff --git a/src/platform/web/ui/css/themes/element/theme.css b/src/platform/web/ui/css/themes/element/theme.css
index 00fdefd0..706bd90d 100644
--- a/src/platform/web/ui/css/themes/element/theme.css
+++ b/src/platform/web/ui/css/themes/element/theme.css
@@ -910,4 +910,22 @@ button.link {
 
 .RoomArchivedView h3 {
     margin: 0;
+}
+
+.UnknownRoomView {
+    align-items: center;
+    justify-content: center;
+    text-align: center;
+    padding: 16px;
+    box-sizing: border-box;
+}
+
+.UnknownRoomView h2 {
+    word-break: break-all;
+    word-break: break-word;
+}
+
+.UnknownRoomView button {
+    max-width: 200px;
+    width: 100%;
 }
\ No newline at end of file
diff --git a/src/platform/web/ui/session/SessionView.js b/src/platform/web/ui/session/SessionView.js
index 214db2a3..c8a77a1b 100644
--- a/src/platform/web/ui/session/SessionView.js
+++ b/src/platform/web/ui/session/SessionView.js
@@ -17,6 +17,7 @@ limitations under the License.
 
 import {LeftPanelView} from "./leftpanel/LeftPanelView.js";
 import {RoomView} from "./room/RoomView.js";
+import {UnknownRoomView} from "./room/UnknownRoomView.js";
 import {InviteView} from "./room/InviteView.js";
 import {LightboxView} from "./room/LightboxView.js";
 import {TemplateView} from "../general/TemplateView.js";
@@ -43,8 +44,10 @@ export class SessionView extends TemplateView {
                 } else if (vm.currentRoomViewModel) {
                     if (vm.currentRoomViewModel.kind === "invite") {
                         return new InviteView(vm.currentRoomViewModel);
-                    } else {
+                    } else if (vm.currentRoomViewModel.kind === "room") {
                         return new RoomView(vm.currentRoomViewModel);
+                    } else {
+                        return new UnknownRoomView(vm.currentRoomViewModel);
                     }
                 } else {
                     return new StaticView(t => t.div({className: "room-placeholder"}, t.h2(vm.i18n`Choose a room on the left side.`)));
diff --git a/src/platform/web/ui/session/room/RoomView.js b/src/platform/web/ui/session/room/RoomView.js
index e2ef0de7..fff875b8 100644
--- a/src/platform/web/ui/session/room/RoomView.js
+++ b/src/platform/web/ui/session/room/RoomView.js
@@ -73,6 +73,9 @@ export class RoomView extends TemplateView {
             if (vm.canForget) {
                 options.push(Menu.option(vm.i18n`Forget room`, () => vm.forgetRoom()));
             }
+            if (vm.canRejoin) {
+                options.push(Menu.option(vm.i18n`Rejoin room`, () => vm.rejoinRoom()));
+            }
             if (!options.length) {
                 return;
             }
@@ -86,8 +89,8 @@ export class RoomView extends TemplateView {
                 },
                 vertical: {
                     relativeTo: "start",
-                    align: "start",
-                    after: 40 + 4
+                    align: "end",
+                    before: -32 - 4
                 }
             });
         }
diff --git a/src/platform/web/ui/session/room/UnknownRoomView.js b/src/platform/web/ui/session/room/UnknownRoomView.js
new file mode 100644
index 00000000..32569d6f
--- /dev/null
+++ b/src/platform/web/ui/session/room/UnknownRoomView.js
@@ -0,0 +1,35 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {TemplateView} from "../../general/TemplateView.js";
+
+export class UnknownRoomView extends TemplateView {
+    render(t, vm) {
+        return t.main({className: "UnknownRoomView middle"}, t.div([
+            t.h2([
+                vm.i18n`You are currently not in ${vm.roomIdOrAlias}.`,
+                t.br(),
+                vm.i18n`Want to join it?`
+            ]),
+            t.button({
+                className: "button-action primary",
+                onClick: () => vm.join(),
+                disabled: vm => vm.busy,
+            }, vm.i18n`Join room`),
+            t.if(vm => vm.error, t => t.p({className: "error"}, vm.error))
+        ]));
+    }
+}