A bomb alert which saw a bridge over the Tyne closed for two hours was caused by a piece of "conceptual art" made of doll parts, a keyboard and a metal cylinder with wires sticking out of it.
Thomas Ellison, 32, left the "suspicious device" on the High Level Bridge not realising it may cause alarm and fear of a terrorist attack.
The bomb disposal unit attended to safely extract the bizarre article, which was a transparent lunch box containing a doll, circuit board and wires.
The "artwork" was stashed behind a pillar on the bridge.
A court heard it was there for three days, despite attempts by members of the public to raise the alarm.
Newcastle Crown Court was told some people tried contacting Northumbria Police by dialling 101 but they couldn't get an answer, but the force have since stressed that 101 is frequently subject to high demand and should be used for non-urgent queries only.
When one woman did get through to report what she had seen, two officers went to the bridge but couldn't find the package.
After when the alarm was raised, Ellison phoned police to say he had left something on the bridge and he was told he should not be using the 999 system for that.
Ellison, of Lynnwood Avenue, Elswick, Newcastle, had been charged with making a bomb hoax but prosecutors accepted his guilty plea to causing a public nuisance, entered on the basis that at the time he did not think it would be treated as a suspicious device.
The artwork was made up of a doll's head and arm with a keyboard for a body and caster for legs.
The arm was holding a metal cylinder with wires coming out of it.
Prosecutor Mark Giuliani said:
The court heard it came to light on Tuesday August 15 last year but it had been there three days.
Mr Giuliani said:
The court heard Ellison then rang police anonymously, saying "I think I may have left something on the bridge which caused some disruption".
Brian Hegarty, defending, said:
Mr Giuliani, prosecuting said: "We say a right-thinking member of the public would consider it to pose a risk, particularly in this day and age. The doll had wires coming out of her back."
Mr Hegarty said:
Ellison pleaded guilty to causing a public nuisance between August 13 and August 16, namely by placing a device resembling a bomb onto the High Level Bridge.
He was released on conditional bail and will be sentenced next month.
Following his conviction, Detective Constable Kim Day said it was "incomprehensible" that the student wouldn't have known the consequences of his actions."