Lisbon - for a capital city it's one of the smaller ones so easy to navigate - excellent reasonably priced public transport. Lots of history and culture to absorb.

If you want a break from the city 30 minutes on a train and you are in Estoril or Cascais which are very pleasant seaside towns - if you like the beach stay there and travel in to Lisbon.

Thanks for the response - I'm on a bit of a mission to visit all the capital cities of europe so Lisbon sounds like a good plan, although if it's not the biggest of capital cities it might be worth staying at the beach and travelling in. Any idea what the nightlife's like? Would I get a chance to go out if I stayed at a seaside resort?

infromation about the best ways to get around Lisbon (definately the 28 tram) is in this thread. http://www.holidaytruths.co.uk/viewtopic.php?f=1&t=138629&start=20

Cascais is at the end of a frequent service commuter line from Lisbon (Cais do Sodre). Trains back from Lisbon run until 01:30 and restart at 05:30 (04:30 after some busy nights) so staying in Cascais and going out in Lisbon is possible. The line has an English information page at http://www.cp.pt/cp/displayPage.do?vgnextoid=bf066e29d6b74010VgnVCM1000007b01a8c0RCRD

Cascais has a good spread of bars and restaurants so you have the choice. It's also well placed for visiting the palaces at Sintra using the local bus run by a Stagecoach subsidiary, the route (403) also serves Cabo da Roca which is a superb view (on a sunny day) along the cliffs from the most westerly point in Europe. Their new website at http://www.scotturb.com may start to work properly soon! Cascais is covered by the same toursit website as neighbouring Estoril, see http://www.estoril-portugal.com/en

Other interesting places in Portugal would be Coimbra (also has a handy beach resort, Figueira da Foz) and Porto but they are in the north and not really day trips from Lisbon. Porto has it's own airport.