Louvre
In Paris, they find extraordinary things in their basements.
When excavating for the Grand Louvre project with I.M. Pei's entrance pyramid, they found the foundations of battlements right where they'd left them. There's a lot of this going around; here's a 16th century porch, unmarked and unremarked (except, luckily, by a delightful Paris Walks by Alison and Sonia Landes).
