Virtual Tours
Many Museums offer virtual tours, ranging from a simple google maps style walk through, video guides, to fully immersive VR tours.
Here is a small selection:
The National Museum of Natural History
The Louvre (Note exhibits are in French)
Renwick Gallery, Smithsonian American Art Museum (Requires Smartphone and App)
The Metropolitan Museum of Art
The National Museum of Computing
Google Street View has a wide selection of Monuments, Palaces, Museums, and Historical Sites to view as well.