The huge and gorgeous Titian, The Vendramin Family, c.1540-c.1560, displays a frieze of males of all ages, three or four generations – and an adorable lap dog held close by the youngest boy – in marvellously sumptuous costume. The painting is surrounded with portraits by an ardent admirer of Titian's, Anthony van Dyck, our interest in the Titian deepened by the fact that Van Dyck once owned it. It is but one of the stars of this fascinating sampling of the collecting habits of artists themselves.

Here comes the Switch House. The 10-story new build attached to the Gilbert Scott Bankside power station that was the first instalment of Tate Modern in 2000 opened to the public this weekend. Tate Modern’s expansion became almost a necessity as the original estimate of two million annual visitors became five million.

Black Brook, 2014, is sublime. Two bands of acid-green grass frame a horizontal band of deep-violet water that appears to have hidden depths. Dotted randomly over the darkness are clusters of light blobs; they could be floating leaves or reflections dancing on the surface. There’s no way of telling. 

As if to signal a coming of age, this year's Whitstable Biennale has a theme: The Faraway Nearby. And so for the first time artists have a guiding idea with which to post-rationalise their work. Until now, the 10-day festival of visual art has staked out broad territory with performance, film and emerging talent. So perhaps an equally broad theme was needed to ensure that works comprised of fan letters, a lecture tour in a car park and a new flavour of ice cream could cohere as a successful biennale.

Pure euphoria! The lady, a mere 87, her stature diminutive, her hair and lipstick a blazing scarlet, is a painter, but also a draughtsman, a sculptor, a creator of environments and installations, a performer, a designer of objects and clothing (affordable too at UniQlo) an illustrator, a writer, a poet, and an all-round polymath. Kusama has lived by choice for nearly 40 years in a psychiatric hospital in her native Japan, working indefatigably.

Cornelia Parker invited over 60 fellow artists to join her in exhibiting at the Foundling Museum in London. Titled Found, the show spills out from the basement gallery to infiltrate every room in the building and remind us that, when the Foundling Hospital was set up as a charity for destitute children in 1739, artists made an important contribution. 

Arts festivals the size of the Venice Biennale are inevitably patchy. The appointed directors are hardly ever given enough time to curate and fill absolutely vast volumes of space. They can exhort the many national and individual participants to follow their lead, and yet they have no editorial control over them. And so for this year’s architecture biennale, with its theme of social responsibility – Reporting from the Front – set by director Alejandro Aravena, consider the newly-built Australian pavilion. This proudly features a swimming pool.

Painted during his first trip to Paris in 1900, Picasso’s Le Moulin de la Galette is an outsider’s view of an exotic and intimidating new world. Men and women are seen as if through some strange distorting lens, their blurred, mask-like faces indistinct but for red-slit mouths and coal-black eyes. We seem to be in the room with them, and yet we are isolated. Even a woman looking out from the edge of the canvas gazes straight past us: if not invisible, we are certainly inconsequential.

Tanya Habjouqa, winner of the World Press Photo Award 2014, is a founding member of the all-female Middle Eastern photography collective Rawiya (meaning “she who tells a story”) which focuses on raising the visibility of female Arab photographers as well as presenting an insider’s view of the region, and defying Western stereotypes of the Middle East.

The second exhibition staged by Damien Hirst in his stunning Newport Street Gallery is of work from his collection by the American artist, Jeff Koons. Hirst was still a student at Goldsmiths when, in 1987, Charles Saatchi showed Koons and other young Americans at his gallery in St John’s Wood. Hirst was blown away by the freshness and ambition of work that took Warhol’s love affair with consumer culture one stage further. This mini-retrospective can be seen, then, as a tribute both to Saatchi and Koons – inspirational figures in the 1980s.