Which software could show all POIs

I tend to use the combination of taginfo and overpass to show where arbitary things are on the map.

First, I'd look for where the thing that I'm looking for occurs as a value. In this case:

http://taginfo.openstreetmap.org.uk/search?q=ridge#values

(I'm using taginfo.org.uk because I want to see examples in the UK; if I wanted to search internationally I'd use taginfo.org).

Then click on "value" which takes us to:

http://taginfo.openstreetmap.org.uk/tags/natural=ridge

and then click on "Overpass turbo", move to an area I'm interested in and run the query, which takes us to:

http://overpass-turbo.eu/?key=natural&value=ridge&template=key-value

In this case there's probably some "mountaineer" rendering on an external map somewhere that shows this info on tiles, but this is a general solution for things that are unlikely to be rendered anywhere.