The Palace of Versailles in France
The legendary Palace of Versailles began as a hunting lodge in 1624. After more than a century and a half of building, which included some of the most impressive construction campaigns in the world's history, toilets were added in the 18th Century.
That's not toilets for the masses, servants or even guests. That's any toilets.
Of course, there were temporaries that could be brought to rooms by servants, or some of the thousands of nobles staying in the palace's 300 plus guest rooms could bring their own comforts, including a portable commode. Some would wait until dusk and rush to the lawn outside, making the scenic walks an unwelcome and smelly place to stroll.
Happily, toilets were added in 1768, a mere 144 years after the original construction. Phew!