Church of the Covenant, an 1867 Gothic Revival masterpiece, has one of the largest collections of liturgical windows by Louis Comfort Tiffany in the country; its 236 foot steeple is the tallest in Boston
I've visited the 9/11 Memorial a couple of times so skipped it on this trip; One World Trade Center (ie Freedom Tower) is still jaw-dropping as the tallest building in the Western Hemisphere (the same architect designed Willis Tower and Burj Khalifa)
The Cooper-Frost-Austin House, built in 1681, is the oldest house in Cambridge; the city of 116,000, home to Harvard and MIT, has 57% of its residents possessing at least a bachelor's degree
We tried to book scuba and snorkeling trips to Molokini and Lanai but everything was booked solid for the next 2 months; rental cars and hotels/condos sold out with international travel for Americans still largely banned