Thursday

Much against our natural impulses, we get up early to shower and wander down to the corner bakery for cheap croissants. The plan is to visit the Norman Foster-designed glass dome on top of the Reichstag building, which is free and hence the guidebooks recommend getting there either early in the morning or late in the evening.

We walk the same route through Potsdamer Platz and the Sony Centre as we had the previous afternoon, both suffering slightly with yesterday's aches and pains as well as the soaring temperatures - but we finally arrive at the Reichstag at a decent time. We are, it seems, not quite early enough though; the queue already stretches around three times longer than the '30 minute wait from here' sign. We decide to try again later this evening, when we won't have to queue in the blazing sunshine, so we walk away from the enormous parliament building towards the heavily-wooded Tiergarten and its odd-looking Chinese bell tower.

As most of the park is fenced off for the FIFA Fan Fest (big screens to watch the World Cup matches on) we end up reaching a bit of a dead end before long, so we decide to turn on our heels and walk towards the massive TV Tower; which dominates the skyline almost everywhere you turn and is as potent a symbol of East Berlin as I can have imagined from reading books. It must have looked fairly terrifying to West Berliners when it went up in the 1960s.

It takes at least an hour to walk to the TV tower on a route that takes us through Museum Island, a collection of incredibly impressive old buildings whose entry fees we baulk at; particularly because neither of us can really imagine walking round a museum in this oppressive heat.

We buy our tickets and head up the lift to the observation deck of the tower - which gives us predictably stunning 360 degree views of the surprisingly compact centre of Berlin, as well as the trains coming and going from the Alexanderplatz station below us.

On returning to ground level, we get our first S-Bahn train (the overground one) out of the city centre towards the Olympiastadion; a piece of undoubted sporting history, having hosted Hitler's 1936 Olympics, and more recently the 2006 World Cup. Walking up to the gates it is undoubtedly a piece of Nazi, Roman-fetishising architecture; but it's scale and impressive bulk is still very impressive. Unfortunately we are unable to go in for a nose around, as the site is closed for an AC/DC concert that evening (we had noticed a hell of a lot of AC/DC t-shirts around; we had presumed it was due to the Germans being such renowned rock'n'roll animals), so we hop back on the S-Bahn to the next stop which hosts, seemingly exclusively, another Nazi spectacle in the Glockenturn (clocktower). This enormous concrete tower is only 3 euro to get into, and so we see Berlin from the sky for the second time. It affords an amazing open-air view of the Olympiastadion and the city centre in the distance, and is actually a much more rewarding experience than the 10 euro TV tower.

Finally we drag ourselves back into the centre via the Hauptbahnhof; an amazing multi-storey train station and quite a feat of transport-hubbery; where we visit a small supermarket to buy bits and pieces for a planned picnic in the Tiergarten. By this time, as should be obvious, we are completely shattered, so by the time we find a decent little patch of grass (not the nicest park, in truth) to eat and drink in, we're more than ready for the rest.

Partially re-energised by chorizo, cheese and Berliner Pilsner, we make our way on foot back to the Reichstag to try again at the Dome. The queue is shorter, albeit made up of a typically obnoxious tour group of American teenagers, so we decide to bear with it and finally get to the top. When we finally get up there - and see Berlin from above for a third time today, the dome is indeed impressive, and there's a fair buzz around as the spiral walkway to the top makes the other people there giddy and excitable. K and I lie down at the top and look at the sky - me basically feeling unable to move another inch.

The plan for the rest of the evening is to try and find somewhere pleasant to sit and drink; so the guidebook recommends a nice canal-side beer garden near the Zoo. We duly get on the U-Bahn again and find - to our horror - that the beer garden is a long, featureless walk from the Zoo station (and actually very close to another, much handier S-Bahn station. Cheers, Lonely Planet!) so by the time we get there K is exhausted and furious - but that first pint doesn't half taste good. Somehow we find it in ourselves to get home, despite almost missing the last U-Bahn at 0030, and collapse, instantly unconscious in our hotel bed.

It's safe to say, I think, that at this point we've done tourist Berlin absolutely to destruction. We're both looking forward to a more relaxed day tomorrow - and a much-needed lie in.