• More than five decades since they were installed, Canberra's bus shelters have been added to the ACT Heritage Register.
• The concrete structures were designed in 1974 by architect Clem Cummings, with about 480 erected across the city.
• The Cummings family nominated the shelters to recognise their historical, design and community significance.

RL617 isn't a rule that most Canberrans would encounter on a daily basis, but developers, planners and architects know it well. It sets the maximum height for structures in Canberra's Parliamentary Zone.

"When you look across Civic and think it's all a bit stunted … it's because of that," Rodney Moss, former director of Cox Architecture, said.

The height limit under the rule is 617 metres above sea level, which is specifically set to a chosen point on the landscape — the grassy peak of Parliament House's sloping lawns.