Parking is usually pretty easy to find in the garages, although with garages closing with increasing frequency that may not be true much longer. Traffic is a problem.
On days that the Haymarket vendors are not operating it gets quite desolate behind Haymarket Station. I'd recommend avoiding this area if alone after dark.
More green space to spend time enjoying; greenway behind Haymarket. Sunbathing and picnicking with Italian food from the nearby North End, such as cannoli and pizza, are common.
The historic Green Dragon Tavern on the left, the historic Bell In Hand on the right, the Freedom Trail running between. These landmarks are not only historically significant but also quite picturesque.