It's beneath the + - here -
There are two buildings that comprise the ruins of the castle, this one the Keep, the other is the Constable's House which you can see tomorrow.
The castle was originally built as a defensive mound topped with a wooden tower at the time of the Norman Conquest, this is all that remains of the stone keep which was built towards the end of the 12th century.
An article (well worth reading in full) on the - Christchurch Local History Society -
web site says :-...the Civil War saw Christchurch Castle still in military use. It withstood a close siege in January 1645. After the war it was slighted and walls pulled down to avoid its reoccupation by Royalist supporters. Hence the castle had military potential for some 600 years and the site has survived for over 900 years.
That's why there is so little left, which is a pity.
Taken last week, this is almost he only bit of blue sky I've seen for weeks, it lasted a very few minutes.
.....If you have a spare moment, please visit my vfxy.