There is, arguably, no greater artist than Rembrandt van Rijn (1606-1669), the Dutch painter who practically invented the truthful, probing and often melancholic self-portrait. He did 70 all told–paintings,

drawings, etchings–and an amazing 60 of them are on view in Rembrandt by Himself at the National Gallery in London through Sept. 5. His paintings of himself from age 23 to 63–with those deep, wet, dark eyes, bulbous nose and vulnerable, pensive mouth–esthetically obliterate all those glaring, tortured self-portraits by all those glaring, tortured artists who’ve come down the pike since. Not that Rembrandt didn’t have troubles: his wife, Saskia, died in 1642 (at which point he quit doing self-portraits for 10 years); he went bankrupt; his lover Hendrickje Stoffels died in 1663, and his only son, Titus, passed away a year before Rembrandt himself died.

Axel Roger, one of the show’s curators, says, “The self-portraits were bought by collectors. You could get, at the same time, a painting, an image of the most famous artist of his times, and a sample of his handiwork.” Not to mention a piece of one of the most long-run, heartfelt and unblinking self-analyses ever conducted by an artist.

As a sheer painting talent, Anthony van Dyck–whose 400th birthday is this year–isn’t far behind. He was almost a neighbor, coming from Antwerp, in Flanders. Van Dyck began painting as the most gifted pupil of the glamorous artist-diplomat Peter Paul Rubens (Rubens himself said so). Van Dyck could do it all: portraits of kings, vast religious scenes and landscapes (although pure landscape wasn’t permitted in van Dyck’s day, so he had to confine it to sidebar status). He did them all with a confidence in drawing and a deftness of brushstroke not seen again until Manet in the late 19th century. Naturally, van Dyck was neurotic, tightly wound and habitually obstinate. But he was such an overwhelming talent that Charles I of England–one of the most splendor-oriented rulers in Europe–invited van Dyck in 1632 to come and be his court painter.

The only troubles were that the London painters’ guild was extremely jealous, and that the otherwise profligate monarch was slow to pay his artist. So van Dyck moved out of the city to Blackfriars, where he nurtured a dream about returning to Antwerp and eventually supplanting Rubens as the greatest Flemish master. But he died at Blackfriars, in 1641. What has returned to the Royal Museum of Fine Arts in Antwerp, however, is a full retrospective of more than 80 works from collections all over the Western world. It runs through Aug. 15.

Two contemporary artists, Ann Hamilton and Annette Messager, construct portraits of an entirely different kind. Installation artist Hamilton, 43, is the official American representative in the Venice Biennale, which stays open through Nov. 7. For her project, “myein” (from a Greek root meaning mystery), Hamilton has totally gutted and redone the U.S. pavilion. (Built in 1930, it looks like a small-town bank in Iowa and could use some updating.) First, she’s constructed a glassed wall across the front of the courtyard. Seen through it, the pavilion practically dissolves. And inside, Hamilton has fashioned–on bare white walls–large Braille texts of excerpts from “Testimony,” a poetry epic by Charles Reznikoff recounting the struggles and sufferings of underclass Americans. To accentuate the texts, a continual rain of fine red powder sifts down along the walls from above.

To appreciate why Hamilton’s piece isn’t merely a collection of pretentious add-ons, you have to be there–and move through it. The somewhat pixieish and very Mid-American Hamilton (who lives in Columbus, Ohio) says, " ‘Myein’ is something that unfolds in time–it’s the approach, then passing in front, passing behind. It’s about rhythms and the fireballs." Fireballs? “That’s when, after the powder descends steadily for a while, a whole ball of it gathers and falls, and goes ‘poof!’ " We think “myein” works, but if you’re skeptical, you can ask Lauren Bacall, Steve Martin or Dennis Hopper, all of whom trooped through the pavilion in the Biennale’s opening days.

Although Annette Messager, 55, doesn’t go quite so far in her installation of personal flotsam and jetsam, “Dependence/Independence” (at the Hamburger Kunsthalle through Aug. 8), she goes far enough. Greatly expanded from her 1970s work, which used mainly toys and needlework, “D/I” employs hundreds of what Messager calls “droplets”–photographs, light bulbs, fabric scraps and stuffed animals–hanging from the ceiling on threads. The piece is a veritable downpour of memorabilia. Messager has said that “obsessive collecting is a struggle against the finality of death.” At this rate, she’ll be around for a long time to come.

Lady Clementina Hawarden wasn’t as fortunate. She died at 42 in 1865, possibly in part from exposure to photography chemicals. Lady Hawarden, you see, was one of the best pioneer Victorian photographers. In 1859 she moved to London–just a few hundred yards from the Victoria & Albert Museum, where a show of her absolutely fascinating pictures runs through Aug. 30. Hawarden used a large-format camera (negatives 10 inches square), the same bedroom as a set (wallpaper, fabric and shadow patterns in crisply varying compositions) and two of her daughters (she had 10 children) in costume. True, there are a lot of swooning females ridiculously posed–in one photograph, a daughter takes the part of an imploring male swain–but this was 100 years before even Betty Friedan decided to escape from the kitchen. Hawarden quickly surpassed the simple wonder of merely being able to take a photograph, and applied a personal, sure-handed sense of design to her art.

Whatever the attractions of portraiture, self-portraiture and family history, there’s still nothing like painting for painting’s sake. Judging from the crowds at the exhibition of Claude Monet’s “Water Lily” paintings at the Orangerie in Paris (through Aug. 2), people still can’t get enough of it. Or maybe it’s Monet they can’t get enough of. Putting a large selection of his easel-size water lilies on the second floor of a gallery built specifically to house his mural-size water lilies below is something like double-chip fudge ripple in dark brown ice cream for people addicted to chocolate. In 1893 Monet (1840- 1926) bought some land adjacent to his home in Giverny; put in a pond, a Japanese bridge and a lot of vegetation; and made its various views his painting subject for the rest of his long life. It’s all masterly stuff: colors, brushstrokes and an evocation of the most pleasant days you can imagine, all daubed marvelously off the cuff. But if anyone has an idea of Monet as some kind of old nature hippie, there’s a charming 1915 film of him in the exhibition–painting in a suit and tie, with a long-ashed cigarette poking through his great white beard.

That cigarette–bent and still smokin’–is a little like the Centre Pompidou not far away. A wonder of late modern architecture wonder only 20 years ago, most of it has had to be closed for repairs. But one corner is still open, to house a surprisingly satisfying Robert Delaunay (1885-1941) exhibition, through Aug. 16. We tended to think of him as a tardy, misguided cubist who tried futilely to turn that smoky, cafe-bound style into something epically colorful. Well, that’s what he did do, but he succeeded more than we thought. Delaunay worked in discrete series (views of Paris, the Eiffel Tower and rugby players), trying to fuse Gallic classicism with a painterly sense of fresh air. Along the way, he indulged his enthusiasm for early aviation, sticking kitelike biplanes into his pictures whenever he could. Before he sailed off into pure abstraction he did a series about a visiting Welsh rugby team. The rugby paintings are possibly his best–bright, tightly composed, with delightful little hints of pop-art signage that would arise in America a half-century later.

Bridget Riley, 68, purified painting even more. She reduced it–or accelerated it–to eye-boggling geometric arrays of stingingly high-chroma color. At first she was just trying to convey a sense of heat rising from an Italian landscape, but soon, she once said, she boiled her art down to “putting the elements of painting through their paces.” Riley’s best paintings were made in the 1960s and ’70s, when she was the queen of op art, and 30 of them are on view at the Serpentine Gallery in London, through Aug. 15.

What Riley aimed for optically–power–is what Richard Serra, 59, aims for physically. “Snake,” one of the works in his enormous show of recent sculpture at the Guggenheim museum in Bilbao (through Oct. 17), is 102 feet long, 13 feet high and 18 feet wide. Its three curving walls are made of 2-inch-thick steel. It weighs even more than the “Torqued Ellipses”–which constitute most of the exhibition and check in at 30 to 40 tons each. “If you were an ordinary person who hadn’t been told what this is, you might not say it’s sculpture,” says Serra, who looks a little like a Renaissance pope and a lot like the football player he was in high school. Serra started on the “problem” of torqued ellipses five years ago; he and an assistant would nail different plywood ellipses to either end of a short wooden axle, and then roll thin lead sheeting onto the armature to create a model for a form which, Serra points out, is not a truncated cone. “It’s something else, an unnamed form sitting around for centuries, waiting to be discovered,” he says.

The result is heroic abstract sculpture offering as many subtleties up close (the sienna velour of rusting steel, the subtle diagonal quilting of the roller marks) as it does startling shapes from afar. With this body of work, Serra has returned to abstract art in general–and sculpture in particular–the dignity and force it enjoyed earlier in our vanishing century.

What Serra does with grandeur, the Italian painter Giorgio Morandi (1890-1964) equals with modesty. At the Estorick Collection–a small, quiet museum in what a local brochure calls “Islington, the real London”–Morandi’s beige-and-gray crockery still lifes demonstrate what painterly wonders can be achieved with constraint. Morandi never painted any larger than he had to, and never painted any longer on a picture than he had to. But in the sky of an intriguing, atypical landscape from 1941, he accomplished something very rare in the history of art: he seemed to have invented a mysteriously new blue. We’d like to think it’s the color of the European sky for a while to come.