Bonjour Susan !
Unfortunately, there is no definitive trick to guess places' gender, or any word gender for that matter.
We compiled a few hints that, though they don't work 100% of the time, can still give you a feeling of what to look for:
https://progress.lawlessfrench.com/revision/grammar/how-to-identify-gender-by-some-word-endings
I hope that's helpful!
À bientôt !
