Map-based theme

Apologies for a basic question from someone who hasn’t even set up their blog yet, but I want to get it right from the start. Hoping someone might help – I’ve searched for ages but can’t find the answer to this…

I want to start a blog that essentially shows photos, with comments, from different locations. I want the blog to have a world map dominating the page, with photos shown as pins on the map, so that the reader can drill into the map and click on the pins, which bring up the individual photos and comments. So, not really different from a custom google map. It can then have the individual entries below the map, and all the other usual widgets down the side – but I want the map to stay at the top of the blog.

Ideally, we could simply take a photo and upload a geo-tagged entry (eg from iPhone – the photos are not artistic ones) that would automatically get updated on the blog and map, although I accept that this might not be possible and I might have to manually add the location information.

I’d be grateful for thoughts and apologies again if the answer is obvious. Even a steer in the right direction would be useful… I haven’t started the blog yet and am open-minded on whether to self-host or not, so either version of WP is possible (or even a different blog platform).

Thanks.