Every pilot should be aware of CAT.POL.H.305. It is a EASA regulation that covers the requirements for an approval that is needed for operations without an assured safe forced landing capability during the take-off and landing phases. If the approval is missing operations of this type shall not be conducted.
Basically, CAT.POL.H.305 covers most take-off and landings performed in alpine regions (e.g. Switzerland). Most off-airport landings and take-off performed outside the H-V diagram would not allow a safe-forced landing. Usually a distance of about 250m has to be free of obstacles in order not to require this approval.