This garage is directly underneath the Seaport Hotel Boston.
Its rates are pretty reasonable, and it's easy to book on SpotHero.
I find this garage easier to navigate than the SBWTC South Boston Waterfront Transportation Center one.
On SpotHero, you may also see the garage of "601 D St Garage" when the commonwealth pier garage is fully booked. The rate is slightly higher, but it's all connected underneath the garage.
If you park at 601 D St Garage, when you get to the building lobby, there are two clean single stall bathrooms for you to use. read more