First was an informal ~1 hour chat with one of the senior CxO level employees over a coffee in a coffee shop that was nowhere near the office.
This was followed up with a 15 minute phone call with a technical person, which appeared to be primarily focused on verifying the quality of the technical skills I listed on my resume.
Next was a 5 hour meeting with about half the board of the company and several external consultants.
The final part of the process was a two hour meeting with a couple of project managers and a junior developer / tech. support engineer. I am not sure about this, but I think one of the project managers might have been either still interviewing for the job or has only just started.