Longwood Gardens is just over the Pennsylvania border, 30 minutes from Wilmington, and is the most spectacular of the Brandywine Valley du Pont estates. Pierre S. du Pont bought the property in 1906 and spent four decades building it into the present 1,100-acre garden — formal terraces, the famous fountain garden with its choreographed water shows, three acres of conservatories, a topiary garden, and a meadow garden through the open hills.
The conservatory is open year-round and is the wet-weather backup; the fountain shows in summer are a serious attraction in their own right. The Christmas display, with the conservatories full of poinsettias and the fountains illuminated, is one of the busier seasonal attractions on the East Coast.
Timed-entry tickets are strongly recommended. Allow a full day if you want to see the conservatory and the outdoor gardens at leisure.