One Sheffield explorer, who did not wish to be named but was on the visits to both Sheffield Cathedral and Jessop Hospital, said: "We normally visit places which are going to disappear and are a part of our history.
"The cathedral was a bit different. It was a unique opportunity to see the city centre from a different perspective. We never damage anything. Breaking in is something we would not do. Our motto is 'take only photographs and leave only footprints'."
"There is an element of risk but we take all precautions we can. It's worth it to see places which are so important and could be lost."
Not the sort of behaviour one should publicly condone, of course - but the pictures are intriguing. The explorer, DBS, notes: You'll find it tough to get in though if your waist is more than 30" and you can't shimmy drainpipes. I suspect I won't be joining them, then.
Latest on Sheffield University's plans for the site -
This next phase will see us refurbish and bring back to life the historic Victorian Wing of the old Jessop hospital building and build a landmark new building on the west corner of the same site.
These developments will provide new homes for the departments of Music, English, Law and History, and provide outstanding facilities for staff and students across the University.
The department of Music will move into the Victorian wing, once the careful refurbishment of this Grade II listed building is complete, whilst English, Law and History will all move into the new landmark building on the west corner of the site.
The new landmark building has been designed by Sauerbruch Hutton, award winning architects renowned for delivering iconic buildings, with environmental sustainability as a top priority. Sauerbruch Hutton won the contract as part of an internal architecture competition held by the University last year.