Where to Find and Catch Hippowdon
From Pokemon Go Wiki
Hippowdon are found and captured in Nest and Habitat locations.
Nests
Hippowdon Nests are locations that consistently spawn Hippowdon.
Habitats
Hippowdon Habitats are spawn locations where Hippowdon is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: