Saint Petersburg

St. Petersburg needs 3 days: the Hermitage (one of the world's largest art museums) on one, St. Isaac's Cathedral and the center on another, and the Peterhof palaces on the third. June-August brings the «White Nights», when the sun barely sets due to the extreme latitude. It's more affordable than Moscow for some services. It was the Russian Empire's capital for two centuries, built from scratch by Peter the Great as a «window to Europe», and its Hermitage Museum holds over 3 million works, one of the largest art collections on the planet.