If you’re in the Quincy Market/Faneuil Hall area, be sure to check out the Holocaust Memorial. It’s on the sidewalk almost in front of the Union Oyster House. Look for tall glass structures with smoky sidewalk grates inside.
On preview, I see Wednesday Evening mentioned it. So go!
If you like architectural space, it’s tough to beat the Trinity Church - Boston Public Library - Apple Store trifecta.
The Copp’s Hill Burying Ground is really moving, too.
If you want nerdy stuff, I highly recommend the Harvard Museum of Natural History. Make sure to look at the glass flowers.
Here’s a little sampler - Suite 101 - How-tos, Inspiration and Other Ideas to Try
Modern and Maria’s are the two that come to mind. Don’t get me wrong, Mike’s is good, but it’s always crowded and a bit noisy.
And the mineral collection. The attached Anthropology museum is also packed with nerdy goodness, especially the top floor, which is an old-fashioned densely-packed gallery of all things Oceania-related, from Australian Aboriginal stone knives to delicate Balinese shadow puppets, with assorted canoes hanging from the ceiling. The first floor is a startling contrast: a very new-fashioned exhibit on Native Americans with music, special lighting and all the latest museum methods.
For cutting-edge nerdiness (and a gift shop to match), don’t miss the MIT Museum, also in Cambridge. For grandly lavish interiors, don’t miss the main Boston Public Library building; it’s almost too gorgeous to read in there.
The Freedom Trail is great, but be sure to focus on the bits most interesting to you (for me, Bunker Hill, Copp’s Hill, the Shaw Monument and the USS Constitution); don’t feel obligated to visit every single spot, especially if you’re pressed for time or the weather’s icy.