Help with Wordpress project…

Hi all, I'm new to OSE and am looking to have a single map on my site (http://mapped.city/map/) which shows the location of all of the tagged Portfolio pages on a single map. Firstly do you know if this is possible for a Portfolio section of WP? And secondly, if it's not, do you know how I can keep adding markers to the same map without it resetting each time?

Many thanks!