A total of £768,000 has been spent on Castle Rushen in the past 15 years.
The money's been spent on stone masonry, maintenance, restoration and conservation work.
The figure was revealed by Enterprise Minister Tim Johnston in response to a written Tynwald question from Arbory, Castletown and Malew MHK Jason Moorhouse.
Mr Moorhouse wanted to know whether Manx National Heritage had invested anything in the attraction's gift shop.
Plans for four-foot flood walls at Ramsey harbour
Garage blaze in the early hours of this morning
Art anarchists "hiding gold bars" in Douglas this week
No cases of terror financing through charities
You can now adopt an ambulance
Case for horse tram tracks 'under final review'
Council spends more than £1m on beads for cavities
Police recruitment drop-in sessions tonight