I decided to do a one day trip to Sintra from Lisbon. I think this is the minimum amount of time you should spend there. In retrospect, I wish I had done two days there - either staying overnight in Sintra town or catching the train back again from Lisbon.

It's a beautiful landscape with so much to see. I found it fascinating to see the evolution of the site from the period of the Moors, through the Medieval years, up to the Romantic 19th century and even into the way Sintra is used today.

There is no doubt in my mind that this is one of (if not the number one) best WHS in Portugal. So it's no surprise that it is incredibly busy. The other advantage of going for a second day is that you can visit some of the areas that are less crowded because the day-trippers focus on the highlights.

Having said that, if you want to see the highlights, I would suggest seeing the National Palace, then Quinta da Regaleira, then the Moorish Castle and then Pena Palace. That gives you a real variety of what's on offer and shows the different historical periods.