Einstein's Chair is an astronomical observing chair from the Old Observatory in Leiden. This chair, made in 1861, is the only piece of furniture in the observatory that dates from that time. The chair gets its name from the fact that it was used by Albert Einstein on several occasions during his visits to the observatory. Einstein was a frequent visitor of the building during his professorship at Leiden university due to his good friendship with the director, Willem de Sitter. The chair can be found in the largest dome of the observatory, the so-called 10 inch dome. (Named after the 10 inch telescope that is placed inside.) The chair is still by observers and a popular attraction at the observatory.