A venue ID is a unique ID for each location on Spacebase. It’s a 4-digits number preceded by #.
After you have logged in to your Spacebase account, click ‘Venues’ in the upper right corner. You should see something similar as in the picture below.
Next to the venue, there is your venue ID.
P.S. Next to the space, there is your space ID. Your space ID can be also found in the URL link or on the space profile, between the main picture and space name.