We'll be arriving in Warnemunde on a cruise and plan on taking the train to Berlin which will allow us only 5 hours to sightsee. As crazy as it sounds I think that the train should make the 2 1/2 hour trip easier. Is it necessary to get a tour guide since we have such limited time. Also, should we purchase our train tickets ahead of time to be safe?

Wow, I'd have a hard time condensing Berlin into 5 hours!

If you look at the "Destinations" tab, above, you can find a link for bus tours of Berlin - the hop on hop off buses leave, I think, right from the main train station. That would give you time for the highlights (2 hour circuit) and at least one stop to see the museum of your choice (there are some amazing museums in Berlin, with the main ones grouped roughly in two major areas - museum island and near Potsdamer Platz).

Spend a little time on Unter den Linden, the main avenue in the former East, with the Brandenburg Gate at one end and Museum Island at the other.

#1 thing to see in Berlin is the Reichstag Building's glass dome. You can see all of Berlin up there.

#2 is the Brandenburger Tor, which is a just a short walk from the Reichstag Building.

You can walk down Unter den Linden from the Brandenburger Tor, passing the Adlon Kempinski Hotel, and continue on to see the State Opera, Gendarmarkt, and Berliner Dom. Museum Island is just a short walk away.

There are lots of souvenir shops along the way if you want to pick up a t-shirt or stuffed Berliner bear.

If you want to go shopping, turn right onto Friedrichstrasse (from Unter den Linden) and wander around Galleries Lafayette.

There are PLENTY of cafes, restaurants, and coffee shops in this area if you want to sit and revive yourself.

There really isn't much to see at Potsdamer Platz--there is the Sony Center, mall, and the remains of the former Wall on display. That's about it.

Thingorjus

I'd go to the Pergamon Museum on the Museum Island. If I remember correctly, you can get to it easily by bus or Ubahn from the Zoo railroad station. The two main exhibits are the Ishtar Gate, from the ancient mideast, and a spectacular temple frieze the Germans acquired from Asia Minor in the 1870's.

Whilst the Pergamon Museum is fantastic (I have been there), I don't know if I would want to spend my limited time in Berlin in a museum. You need two hours to do the Pergamon Museum. Only go if you have wanted to see the Pergamon Altar all of your life.

And if you have come to see Berlin, the Pergamon Altar really has nothing to do with the city, in my opinion.

Thingorjus