Just once a year, a nature reserve in North-West London opens its gates to the general public, at just the right time to see an entire wood carpeted with bluebells.
For just one day, lots of venues will all join together to do lots of things, meaning that even with the fastest feet and most fortunate timing, you're bound to miss out on most them.
A large scale exhibition is currently on at the Guildhall in the City of London remembering the battlefields of WW1 in France, and the contribution made by the "doughboys" to the European war.
On the edges of London, within earshot of the M25 can be found a most marvelous museum, housed in an ancient barn.
For people of a certain age, there are few more nostalgia boosting views than a room full of flat beige boxes, each with a small dot matrix owl on the top corner.
"It's difficult to understand the history of Britain, if you don't understand the history of the British Army", Janice Murray, Director General of the refurbished National Army Museum, said at its reopening.
One for your diaries, as this year's open days to go underneath Reigate town center into its maze of caves have been announced.
A small exhibition has opened, with a gigantic model of a 1960s era tower block.
A feast of colour and decoration awaits at an exhibition of traditional embroidered textiles from the lands of the Indus, Afghanistan, the Near East and Central Asia
A display of mechanical marvels opens at the Science Museum and leaves the viewer with mixed emotions about the blurring boundary between man and machine.
Behind a closed door in an anonymous house on a posh garden square lies a prodigious display of modern craftsmanship.
Over this weekend, there's a chance to go down to the bottom of one of London's canal locks, while it is being drained for maintenance works.
Just over four years ago, a bright morning had me up at the top of the Shard for a look. Time to go back for another look.
The semi-annual Open Doors event is back, offering a peek behind the hoardings that cover up building sites.
Big guns go bang bang several times each year in London, at the Tower of London and in the Royal Parks.
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