Dover has plenty of history that you can explore from a Roman house to the Castle high above the White Cliffs through to the 2nd World War.
The Tourist Information website is http://www.aboutbritain.com/towns/dover.asp, and has links to all sorts of activities, hotels, Bed & Breakfasts, things to do (the list at the bottom, not the left) including animal parks, art museums, cinema, theatres etc.
Hope this helps,
Alan & Katrina
Last Cruise: P&O Britannia March 2015
Next: Minerva April 2015
Then: Royal Princess August 2015
and : Queen Victoria January 2016