Castle Rushen will get a new drawbridge, if planners grant its owner registered building consent and planning permission.
Manx National Heritage says it wants to make major changes to the site's visitor shop as well as improve access to the main keep.
The organisation has applied for permission to create a new shop in the 14th century gatehouse to replace its current facility.
But MNH says the work will be sympathetic to the castle's unique history and won't damage any stonework.
In its application, Manx National Heritage says the existing drawbridge linking the keep to the outer gatehouse is nearing the end of its useful life.
A new bridge would be built from weatherproof steel with timber decking, using a non-slip surface.
The new shop would be able to accommodate larger groups, and designed so features can be removed in future without leaving a trace.
Meanwhile, a new ramp would give visitors better access to teh keep's ground floor exhibition areas.
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