'The Broom Sanctuary' as most members of the Rookou family jokingly call it, is a mahogany shed in which the family brooms, and Quidditch sets, etc. are kept. Caecey Rookou-Greengrass used to sit in this shed and polish the handle of her broom, and clip any bent twigs on them until they are of perfect condition. There are the 'old school brooms' that are passed on throughout the family for those too young to own their own - of which there are none at this current time. It was built by James Rookou I, another one of his 'projects' that he claimed to have built himself - but in reality hired yet another Muggle architect to build it for him - and has been kept in perfect condition over the years. It is regularly dusted by the house-elves, and is still a favourite haunt of Caecey herself, as she, even now, tends to take very good care of her brooms. The various wood splinters on the floor used to be the broom of Ciaran Rookou-Greengrass, and even a slightly aging broom that appears like it may have belonged to Arcturus Rookou himself. There may be a broom that once belonged to Tulula Greengrass that she kept from her childhood, but this is in doubt, since Tulula herself was never really a Quidditch person. You may be asking why Ciaran's broom is in splinters and Caecey's is not. This is another thing that shows the difference between the "defection" of Caecey and the "dereliction of duty" of Ciaran, at least in Arcturus' opinion.
In the usual "buy things to prove we can and then forget about them" Rookou style, at least a couple of examples of every iteration and generation of broom on the market can be found, cobweb covered, somewhere in here. If one has the patience. And lung capacity, as the must and dust are both potentially overwhelming.