Essentially any negative of any size can and probably has been enlarged to mural size in the past. The biggest enlargements I have personally seen and done with another darkroom worker were single piece colour prints with a finished image of 6’ high by 18’ wide using Kodak 72 inch wide by 100 feet rolls.

Ilford had 48” wide by 100’ rolls in B&W paper.

The colour paper processor we had was 76” wide, which didn’t leave much room for misaligned paper. This was an Australian made processor

Our widest B&W processor was 54” wide and made by Dupont in the USA.

Agfa did have a B&W paper, which I believe was 1.4m wide by 30m long, although I’m not sure on the 30m long bit. We never used it but it was offered to us for trial.

All of these papers were RC papers.

The enlargers we used were horizontal DeVere 10” by 10” and all movements were done with a cable remote unit, often in complete darkness, apart from the glow of the enlarger controls. Turning lights on stuffed you up for focusing for at least 15 minutes, so total darkness it was.

Steel walls were used and large strong magnets were used to hold the paper in place. You haven’t lived until you have pulled out in total darkness 6’ wide colour paper and had to hold it (carefully) so that your co-worker could slice the paper in a reasonably straight line a hand width or so away from you! The you had to place it on the wall in the correct position without any saggy bits.

If you were supplied with a transparency, you had to make a negative to enlarge from. If the original was a 35mm colour slide or B&W negative, you had to make a 4x5” or 8x10” negative to enlarge from, this could take half a day or longer to get the planets to align, so that you had a workable, sharp and dust free negative.

Big stuff wasn’t cheap, think thousands of dollars.