MPS Magnet
The spectroscopy magnet in the Multiparticle Spectrometer facility at the AGS at BNL.
The large water cooled "C" magnet has a gap over 4 feet with an area of 4 by 15 feet with an average field of about 10,000 Gauss. You could physically feel the field if you were inside when it was switched on... and wearing magnetic materials nearby was forbidden.
The gap was filled with an array of detector elements to measure the position of charged particles created by the collision and whose tracks were bent by the magnetic field.