The Besieged Tower is a two-level dungeon in Act IV of Diablo III, but is only available in Adventure Mode. It is accessible from Gardens of Hope 2nd Tier, where its radiant teleporting entrance mechanism is like others accessing different areas of the High Heavens, but its location within the Gardens is similar to that of a Hell Portal from Campaign Mode. It also has a waypoint at the start of Level 1.
Bounties are sometimes offered to clear its second level, or to kill several Unique Monsters housed inside. Unlike most "dungeon bounties", this one specifically names level 2 in the bounty label on the map.
Like the Realms of Fate, this is one of the areas added to ensure Adventure Mode has a similar number of areas and Unique Monsters in each act, since Act IV is shorter than others in the campaign. Its appearance is overall identical to the Silver Spire.