What you see, then, is a delicate, fragile-seeming enclosure, which brings the landscape into the interior and vice-versa. It is quite clearly a modern reworking of the idea of the orangery, but draws some of its inspiration perhaps from the humbler kitchen garden glasshouse. When I saw it, it was left almost bare but for three small Hepworths: next year it will stage an exhibition of one of today's leading sculptors, Eilis O'Connell. The gallery takes its place as an incident in the landscape - almost a sculpture itself, like some of the artist-designed bowers that Bessborough places strategically around the grounds so that visitors can rest and take in the views.

Thus refreshed, take a plunge back into city life again and try a new urban arts centre. In Manchester, ambitious plans to extend the City Art Gallery by Sir Michael Hopkins are only now just starting to be built. But walk on a couple of blocks south-east from there and, on Portland Street, you will come across the recently opened Cube Gallery by Stephen Hodder of Hodder Associates. Inserted into one of the city's big old commercial warehouses, Cube is a typically understated but spatially sophisticated series of interiors by another successful example of the new breed of modernists. The gallery's snappy name turns out to be an acronym - the Centre for the Understanding of the Built Environment. It is an architecture and design centre, one of an expanding network of such places that already includes London, Bristol and Chatham, to be followed by Glasgow next year, and with plans for Birmingham in the pipeline.

However, this is a gallery that can be turned to any use. The opening event is curator Victoria Thornton's touring Portable Architecture show, as previously seen in London: but downstairs a rather fine display of entirely non-architectural photograms by Graeme Cooper, curated by Cube's director Graeme Russell, demonstrate the place's intention to step outside its remit into the wider arts world from time to time. One of the spaces right at the front - "the Now Gallery" is devoted to Manchester itself and the changes happening there, as a public resource.

Hodder has done what looks very simple but which is in fact extraordinarily difficult to get right - to strip the building back to its bare brick, iron and timber structure, to bring daylight into the previously dark interiors and basement, and to add a minimum of new interventions. Smooth white surfaces are set against the rough found materials so that old and new achieve equilibrium. I happen to have seen this building both before and during its transformation. It may all seem effortless and inevitable now, its four galleries, seminar room and bookshop making a logical interlinked sequence on two levels - but it used to be a very dreary and confusing place indeed.

Cube is run by a trust. It works on a shoestring, like many other Lottery-funded projects - yet has the energy to produce not only exhibitions but also its own magazine, to take the debate about the shape of the city to a wider audience. Funding will no doubt continue to be a problem - it always is in such places. Hodder's interiors, however, are very adaptable. This place could turn into a private art gallery, even a restaurant, if need be.

The Cube Gallery is necessarily inward-looking, a place to discover within an urban block. Roche Court's New Art Centre, in contrast, is an extrovert, its main mission being to look outwards and be seen in return. Both repay a visit. Neither of the architects involved - Hodder or Marshall - has yet succeeded in winning one of the world's big landmark art gallery commissions. Still: someone's got to design the new Hayward, haven't they?

Munkenbeck & Marshall's New Art Centre at Roche Court