A 30m section of Chester city wall has been cordoned off after part of the ancient monument collapsed.
A team of surveyors, engineers and archaeologists is investigating after part of the wall alongside the Grosvenor Hotel collapsed on Thursday.
Chester City Council said a section of the walls walkway had been closed in the interests of public safety.
Diversions will be signposted and access to the Eastgate Clock will not be affected.
The walls are a Grade I listed building and are the most complete city walls in the UK.
They form a 2m (3.2km) circuit around the city centre and are a major tourist attraction as people flock to walk them.