SPG points at the Park Lane in London is the way to go. 10k points a night and buy 4 nights get one free.

I would consider purchasing a room in Berlin, they aren't that expensive.

If you have any hilton points, the Denaube Hilton in 10k points a night in Vienna, it is a little outside of the city, but a good use of points. If you get the 2 hilton credit cards, (visa and amex) it would be enough for 2 free nights.

If you add Prague, there is a Holiday Inn Express downtown for 10k points a night.

That is all I came up with so far.

Venice is usually very expensive, I stayed on the mainland and took the train into the city.

Enjoy your trip

Timo
Business Student in Paris, France