The universal qualities we look for are:
There are two main types of venue we need too:
Venues for lecture-style events
These need to be central to a large geographical area and especially easily accessible, and cater for a larger number of people (at the last such event with Joel Williams we had 60 participants in attendance; I'd like to be able to take more than this next season). We don't tend to need an attached farm for lecture-style events in the same way that we often do with workshops/courses.
Venues for smaller groups engaging in workshop events
Workshop events can be one-day or multi-day but in either case there is usually groupwork and a key focus is building networks, so it is helpful to have a diversity of spaces, or sufficient space in a main hall for groups to separate out into different corners etc.
With multi-day events we tend to remain together in the evenings when possible, further building relationships (and minimising costs) by preparing and sharing a meal together as well as sharing our own experiences, knowledge and resources - so it is helpful to have catering facilities which make this easy, either at the venue or attached to group accommodation.
Depending on the subject matter, it is often necessary to either base these events at associated farms (where there is a commitment to the regenerative ethos and particular aspect under study), or have such a farm within easy striking distance.