Aberconwy House, on the corner of Castle Street and High Street, is the sole surviving medieval merchant's house in Conwy, and probably dates from the early 14th century. That makes it older than almost anything else in the walled town except the castle and walls themselves. The National Trust manages it, and different rooms in the house have been furnished to represent different periods in its history, from medieval merchant to Victorian shopkeeper.
It is a small property and a visit takes perhaps 30 to 45 minutes, but it is genuinely atmospheric — the low ceilings, uneven floors, and small windows convey something real about domestic life in medieval Conwy that the castle, for all its drama, does not. The location in the heart of the old town makes it easy to combine with Plas Mawr next door.