Catherine Palace

Catherine Palace is located in Puskinsky district of Saint Petersburg. It is 2 hours away from the heart of the city, but it is worth it. The ticket price is 5 to 7 euros.

Normally, it will take you 4 to 5 hours to see the whole palace with gardens and other buildings around it. There will always be a long queue of people who wants to see the inside of the palace, usually it will last 1.5 to hours to reach the end of the queue, but you can always roam around see the garden and some small buildings. 

You can always find private tour guys, but I recommend wandering by yourself. 

PS. Be sure of the sunny weather when visiting this place.