Thanks for
your comments, they are helpful. I try to summarize:
1. The definition of monument is
broad and may differ in different countries. It may, or may not, include
archaeological
areas or historical
sites.
2. We must provide clear warnings
to participants that they should not enter private property without asking
permission from the owner.
3. In some cases the information
about their location may be restricted for security reasons. How to deal
with it should be negotiated with the institution responsible.
Vicenç