Park Crescent is an elegant, curving terrace of houses just off Marylebone Road. It was designed by John Nash, and built between 1806 and 1821 (thanks to a break of some years after the original builder went bankrupt). Across the road, there was to be another crescent, forming a circus; the financial problems dogging the first development meant the other half was never built and the land became Park Square instead. Similarly, the centre of the circle was to have held a parish church but became Park Crescent gardens.
If you were wealthy enough to afford one of these townhouses (on a 99-year lease), you would have two things. The first was exclusive access to gardens in the crescent and Park Square; the second was a nursemaid to look after your children.What you didn't have was much enthusiasm for you and your children having to cross the very busy road between the two gardens. They are therefore linked by a tunnel; its gentle, sloping approaches are perfect for prams.
The Nursemaids' Tunnel is still in use, linking the gardens which remain private. As a result, the public rarely get to see it - but it is accessible during the annual Open Garden Squares weekend. There are other attractions for the London history-lover here, too.
A pair of plane trees in Park Crescent might not seem terribly exciting at first. After all, the London plane can be found throughout the city thanks to its pollution-resisting properties. These, though, are Waterloo planes, so called because they were planted in 1817 to commemorate Wellington's victory over Napoleon.
Nearby are two small octagonal structures, with another across the road in Park Square. These appear to be small summer houses, with seats set into niches. Why, then, can garden users not go inside? The answer may be guessed from the roundel just visible behind: they are in fact ventilation shafts for Regent's Park underground station.
During Open Garden Squares weekend, I also visited Garden Barge Square (photos on Facebook or Flickr).