This nook of the South End, radiating out from the corner of Tremont Street and Clarendon Street, is a destination for romantic brunches and dinners. Aquitaine, which has been holding court here since 1998, is part of the reason. The French bistro covers all the essential territory, with a luscious soupe à l’oignon gratinée, steak frites, and sole Meunière. It serves up a large menu of brunch items on weekends 9am to 3pm, with an elegant atmosphere to accompany such options as Omelette Alsacienne, shrimp and grits, and malted Belgian waffle. Stroll afterwards to Union Park, a block south—brick row houses surround a small oval park, one of the prettiest settings in the city, with a lawn, trees, flowers, and two bubbling fountains.