On first glance it appears to be an unremarkable street, largely given over to residential accommodation. If you happen to find yourself in the area, take a closer look at numbers 23 and 24. They look almost identical to their neighbours, but a closer inspection will highlight their oddly blackened windows and the lack of letter boxes on the front doors.
These minor details are a direct result of the fact that 23 and 24 Leinster Gardens are not prestigious addresses, but merely facades, constructed to hide an underground railway vent. The vent was used to clear the tunnels of smoke when the tube was steam- powered, and preserve the street's upmarket appearance.
They were constructed around the 1860s, about the same time as the underground and in the 1930s became the subject of an infamous hoax. One enterprising one spark sold tickets to a ball at this well-to-do address. Buyers turned up in full evening wear, only to realise the address didn't exist!