Hi and welcome!
It’s an interesting topic, boundary markers have been discussed previously. I would be careful with anything that is considered single-family private residential property, including some farms, as per [quote=“NianticTintino, post:1, topic:12462”]
Single-family private residential properties (SFPRP), **farms**, and K-12 (schools or facilities primarily focused for persons under 18 years of age) are ineligible. This includes the outer facing facade, fence of these locations, and property boundaries.
[/quote]
In general, historical remains without markers are difficult but can potentially be eligible. I would consider them to be similar to ruins, which we have a clarification for
[quote=“NianticTintino, post:1, topic:12491”]
**Ruins**
Ruins that are historically significant, preserved for heritage or tourism, and safe to access can be great places to explore. Submitters should provide context and information in their titles, descriptions, and supporting information. Referencing historical registries and news articles can be helpful when it comes to verifying your claims.
Ruins with no sign, but that are well-maintained and safe to access can be considered eligible.
[/quote]
Cultural heritage is too broad of a topic to make blanket statements. I found this topic that might be helpful:
https://community.wayfarer.scopely.com/t/help-with-spot/111381