As essential work continues, Pontefract Castle will be closed for two days next week to ensure safety on the site.
Contractors will begin work to prune and remove trees overhanging the main drive to the inner bailey, which means the castle will be closed on Tuesday 3 March and Wednesday 4 March.
As part of the £3.5 million Key to the North project, trees including self-seeded saplings, diseased trees and those which are damaging the monument, are being removed to open up the site.
Cllr Les Shaw, Cabinet Member for Culture, Leisure and Sport, said: "We will be trying to keep the castle open as much as possible during this project.
"Safety of our visitors and staff is paramount and this means there will be times when we have to temporarily close the site in order to ensure that there is no risk to the public. We will re-open as soon as it is safe to do so."
The work to the trees and undergrowth has been timed to coincide with the end of the bat hibernation season and before bird nesting begins.
Pontefract Castle has been awarded funds from the Heritage Lottery Fund (HLF), English Heritage, EPaC landfill charity, the Wolfson Foundation and Wakefield Council for the £3.5 million Key to the North project over the next four years. The project will result in the castle being taken off the At Risk register, a new visitor centre with a learning zone, exhibition space, shop and café, restored Victorian paths and many more features. There will also be a programme of events, activities and educational sessions beginning this year and lasting until autumn 2018.