Prague's national gallery is spread out across different locations in the city, the largest collection housed in the Veletržní Palác in Prague 7.
Veletržní Palác has a nice mix of both international and Czech art, as well as random things like this red vintage Škoda.
Some of the big names you'll find in the gallery include: Rodin, Mucha, Manes and Picasso.
While I was visiting, Alfonse Mucha's Slav Epic was on display, which I would definitely recommend seeing if it is still on display when you're there.
With over 2000 exhibits you can definitely spend an entire rainy afternoon strolling through the gallery!