There's no end of museums in Baltimore, including the first one in America that was built as a museum.

The PEALE MUSEUM at 225 Holliday Street (near City Hall) was built in 1814 by painter Rembrandt Peale as the "Baltimore Museum and Gallery of Fine Arts," and remains true to its original purpose. It is first of all a museum about the city, which is to say about the rowhouses that are its heart and trademark. Re-creations of typical rooms in homes of various ethnic groups give a glimpse of what lies behind all those scrubbed marble steps.

The fine arts part comes on the third floor, which is packed with works executed by half-a-dozen generations of the fabulous painting Peales. Go early, because you'll want to stay late. 301/396-3523.

The BALTIMORE MUSEUM OF INDUSTRY on Key Highway (on the way to Fort McHenry) calls itself "a working museum for a working city," and indeed it is. Located in a ramshackle building that once housed one of the first canneries in the country (1865), the private museum is a hands-on, this-is-how-it-works place that will particularly appeal to youngsters. It's staffed largely by volunteers, whose enthusiasm is catching. Open 10 to 5 Saturdays, noon to 5 Sundays, and weekdays by appointment. Admission $1.50 adults, $1 students and senior citizens, 75 cents for children. 301/727-4808.

Of course, a place you've gotta go is FORT McHENRY, and you might as well pack along a picnic lunch, because you'll work up an appetite getting into the batteries by the roundabout route made necessary by restoration work on the main sally port. Fort McHenry has a small museum and is federal and free, of course. Open 9 to 5 every day (9 to 8 Memorial Day to Labor Day).

The MARYLAND SCIENCE CENTER on Light Street near the Inner Harbor is fascinating, but it's not a place to just drop by because the admission's pretty steep: $3 adults, $2 senior citizens, students and military personnel, $1.50 children under 12; family rate of $8 admits two adults and up to four children. It's worth it, with super exhibits, frequent live demonstrations and a number of experiments for kids to perform themselves. Open 10 to 10 Fridays and Saturdays, noon to 8 Sundays, 10 to 5 weekdays; from June 28 through Labor Day the hours are 10 to 8 every day. 301/685-5225.

The FLAG HOUSE at 844 East Pratt Street is where the Star Spangled Banner was not sewn by Betsy Ross. The Fort McHenry flag was made, of wool, by Mary Pickersgill, under a federal contract that was finished on time and within budget. The 30- by 40-foot flag was too big to assemble in the workroom of the 1793 house, so she's said to have carted it into the basement of a brewery next door for the final stitching. "I imagine it was just one long siege of nip-and-tuck, nip-and-tuck," says tour guide Ruth Fader.

Open 10 to 4 Tuesday through Saturday, 1 to 4 Sunday. Adults $1, 12 to 18, 50 cents, under 12 free. 301/837-1793. The SHOT TOWER at 801 East Fayette Street is the sort of structure that, in any city but Baltimore, would probably have been torn down years ago. From 1828 to 1892 this soaring mass of more than a million bricks was used to produce chilled shot by pouring molten lead through a sieve, which then hardened into round pellets as it fell down a long chimney-like passage and into a water tank. A sound- and-light show re-creates the process, or will when they get the bugs out of the computer-controlled device. It's open daily 10 to 4, free and fun. 301/837-5424.

The MARYLAND HISTORICAL SOCIETY at 201 West Monument Street has a lot of neat stuff from the state's early days, but what you're looking for is the Radcliffe Collection of ship models. Open Tuesday through Saturday 11 to 4, Sunday 1 to 5 (summer hours vary). Admission $1.50 adults, $1 senior citizens, 75 cents children, $4.50 per family. 301/685- 3750.

Baltimore has two great art museums that will not bear brief description nor brief visits:

The BALTIMORE MUSEUM OF ART at Charles and 32nd streets embraces old masters to contemporary works, including the Cone Collection of paintings by, among others, Monet, Cezanne, Matisse and Picasso, plus a powerful sculpture garden. Open 11 to 6 Saturday and Sunday, 10 to 4 Tuesday through Friday. Admission $2, under 18, free; no charge on Thursdays. 301/396-7101.

The WALTERS ART GALLERY at Charles and Center streets, embraces works from ancient Egypt through the early 20th century. Open 11 to 5 Tuesday through Saturday, 2 to 5 Sunday, 1 to 5 Monday. Closed holidays. Admission $2 adults, $1 students and senior citizens, under 18 free; no charge on Wednesdays. 301/547-9000..