The colloquia Ehrenfestii take place about once every month. This lecture series has been running since 1912.

After each Ehrenfest colloquium, the speaker signs the famous signature wall, which used to be part of Paul Ehrenfest's house, and can now be found in the Oort building in Leiden. Famous physicists that spoke at the colloquium include: Einstein, Bohr, Pauli, De Sitter, Planck, Oort, Schrödinger, Zeeman and Maldacena.

For current and historic schedules, click here.

For reservations, click here.

For livestream and videos of previous lectures, click here.