image mapper with overlay

Hello

I have an office park map as a graphic on an WP based site and I need to have the visitors select an office block and have the main details come up as an overlay when the particular block is moused over. I can use an image mapper to add hot spots to the individual office blocks and link to an new page but before taking then to a new page I would like them to see an overlay of the main features. Any suggestions?
Thanks
Charles