Lisbon

Lisbon is a nice enough capital city. The central area lacks the insane drivers and overwhelming traffic that plague Rome and other cities in southern Europe, and it is more compact than Berlin - if you don't mind a bit of walking then everything you would want to see in a short stay can be reached by foot. In terms of architecture the centre is fairly uniform, which is not surprising since it was rebuilt as a job lot after the previous centre was flattened by earthquake and subsequent tsunami in 1755. Even the buildings on higher ground seem to have been built in sympathy with the house style until very recently. The overall effect is quite pleasing, like a single giant monument you can spend a whole day wandering around.

The city itself is not loaded down with must-see attractions. Apart from spending a day just looking round the streets, there are a couple of museums and art galleries, and there are doubtless hundreds of churches for people who can bear to see another one. The only really big attraction in its own right however is the castle. This will cost you a little to get into, but is worth it for the view, and the fact that it is the finest place to catch the sun in the whole city.

If you are in the area for more than a couple of days, the best bet is probably to look at towns in the surrounding area, such as Sintra. Since Lisbon is the heart of Portugal's public transport network, you could even remain in the high quality accomodation here and explore half the country by day trip.