The A Street Park is another small green gem in South Boston, nestled in the ell formed by the State Street Building and the new parking garage. It has gentle grass slopes, curving pathways, and plenty of playing surfaces for those proverbial “children of all ages” who live in South Boston. A crowd of perhaps 100 or more showed up for a coffee-and-doughnuts mid-morning fete, on one of the few sunny May days we’ve had recently. In his remarks, Mayor Marty Walsh spoke of “green space” plans, echoing the “Emerald Necklace” concept of Frederick Law Olmstead 150 years ago. With Councilor-at-Large Michael Flaherty and Rep. Nick Collins, and accompanied by a boy named Jack, Walsh unveiled the Park’s sign.