Rome's 1st university, also known as "Università La Sapienza" is
known for being Europe's largest university with 400,000
students
Not sure about the above. According to
http://en.wikipedia.org/wiki/World's_largest_universities, it's
only 147,000. The Open University is considered one of, if not, the
largest University in Europe but it's difficult to gauge.
The open University isn't really a 'bricks and morter'
university, most of their students are home study.