During the summit, the whole city was on heightened alert.
Tips
memory
森严 literally 'forest-strict' - like trees packed so tightly that nothing slips through. Pair with 戒备 ('precaution, guard') to get 'tightly packed precautions' = heavy security.
register
Common in news and formal writing, especially about government sites, summits, high-profile events, and prisons. Rare in everyday speech.
