How do you burn/destroy buildings

Same here - was playing Strongholds scenario, and been sitting inside enemy stronghold for few turns and nothing. Is there any specific way to destroy it? Any other conditions? Was looking eveyrwhere for the answer

It may be a bug, as in one of Game Walkthrougs on youtube I've seen that it was automatically destroyed at the beginning of the turn, when you are in an enemy stronghold.

Please let us know