I highly suggest checking out Natural Atlas (https://naturalatlas.com/) by the same small team who made the CoTrex app (https://trails.colorado.gov/) for Colorado Parks and Wildflife. A really fantastic team building some absolutely gorgeous topographic basemaps from publicly available data. Hopefully they'll find time to add a slope angle overlay at some point. - Source: Hacker News / over 1 year ago

I highly suggest Natural Atlas. The cartography is impeccable and they’ve been adding features over the last year. Source: almost 2 years ago

Try a recreational-themed map like naturalatlas.com. They will list most all known trails. Source: about 3 years ago

Roamaround.io is a basic version of this. Source: 12 months ago

Roamaround.io -It allows you to select your destination city and provides you with a comprehensive travel plan that covers everything from must-see attractions and landmarks to local restaurants and cafes. The platform uses advanced algorithms to curate personalized itineraries based on your interests, budget, and travel preferences. Source: about 1 year ago

I recently heard of roamaround.io for making travel itineraries. I haven't used it to plan any trips yet but thought I'd give it a shot for Iceland this Spring. Source: about 1 year ago