The imminent opening of the Express Rail Link continues to attract much attention.
A latest turn has people thinking there's something mysterious about the immigration co-location arrangement at the West Kowloon station.
In question is part of the terminal building, which was opened to the public last week.
Probably because some staff-only areas are off limits to visitors, claims circulated about a "secret" floor at the lowest level, B5. The mainland has control of the two floors above it.
The rail operator and the government explain there is nothing secret about that floor, which is for maintenance use and as an emergency fire escape. Most infrastructure facilities have such levels, with Chief Executive Carrie Lam Cheng Yuet-ngor saying B5 can be likened to a "back of the house" facility at a hotel.
That explanation was offered after descriptions of the "secret" level had become rather graphic with talk of interconnecting and narrow passageways.
Yet this B5 level is a necessary feature.
As the Hong Kong section of the link was built almost entirely underground, costs have been high. And for facilities used only by staff the costs and space are a major consideration. It's as simple as that. But you can't really blame people for speculating about dark corners and the like.
When I visited Hong Kong Observatory last year director Shun Chi-ming said there was a tunnel that connects to the foot of the adjacent hill.
Was it built because the observatory had some strategic value? Those who are interested could put the question to staff on its next open day.
Back to the rail link and a rather large space inside the West Kowloon terminal that seems to have no apparent use. But it does, or it will have.
The mainland's express system has multiple tracks that can be used alternately when maintenance is being undertaken, so trains can run without interruption at any time of the day or night.
The local section has only one track, so certain times have to be set aside for maintenance work.
But when service becomes more frequent additional tracks will have to be built, and the present empty space near the terminal is reserved for that purpose. But tracks will not be laid until necessary because of cost considerations.
For those who do not know this background the vast empty space leaves much room for the imagination to run.
Siu Sai-wo is publisher of Sing Tao Daily