First I was speaking to a recruiter, just a few words. He arranged a phone interview (which consisted of mostly technical questions).
They said it was successful, so we arranged two on-site meetings in their office.
The on-site interview took 3 hours, one hour technical consultation with an architect, then 2 hours speaking to an HR guy.
I did not like it because we did not agree it will be this long (only an hours), plus the staff was highly disorganized (they did not know whom I was when I arrived, no one was expecting me despite the arranged interview, they didn't have a clear glass I can have water in, the meeting room was occupied, in the office there was stuff everywhere)