The longest mov­ing refract­ing tele­scope is 21 meters long with a lens diam­e­ter of 68 cen­time­tres. This giant tele­scope was built in 1896 by Dr. Frei­drich Simon Archen­hold but is now part of the Deutsches Tech­nikmu­se­um Berlin. It was the place where Albert Ein­stein pre­sent­ed his The­o­ry of Rel­a­tiv­i­ty to the pub­lic in 1915.