[alexsilver]

That is mostly because the "degree of relevancy" is highly subjective in travel and is never constant as places adapt new tourism strategies, new things get built and open. Plus, if you think about it, most world's destinations have pretty much EVERYTHING in each category of travel, if you look hard enough. Sure, some things may receive greater focus but in the end you can find something to your fancy pretty much anywhere you go.

To contrast this with music, where a song will always stay the same and the 3 minutes of it are, arguably, easy to deconstruct into components, classify by genre/rhythm/artist/etc., and then index.

Disclaimer: we too are building a "trip planning tool" but I think we've found a good angle to approach the problem with to avoid the situation most "inspiration"/"social"/"planning" travel startups find themselves in.