Shir Qaleh (Lion Castle) stands near Shahmirzad, on a ridge commanding the road between the Alborz passes and the plateau. The fortress was originally constructed under the Tabaristan government, which administered parts of northern Iran during the Arsacid period, and its purpose was to guard the branch road that diverged from the Silk Road here. The position made strategic sense: this narrow corridor through the Alborz mountains was one of the few practical routes connecting the Caspian coast with the interior.
The Ismailis — the same group centred at Alamut in the Alborz further west — occupied Shir Qaleh in the twelfth century and used it as one of their regional strongholds. Despite centuries of exposure and occasional conflict, the walls, towers and main fortifications are relatively intact. The castle is part of a cluster of historical forts in the Qumis region and is considered one of the more important surviving examples. Getting there requires a short walk from the road near Shahmirzad; the views across the valley from the ramparts are an additional draw.