Layover in Lisbon
 

I have an opportunity to grab a cheap flight with a 19-hour layover in Lisbon, from about 9:30 pm to 4:30 pm the next day. What do you think? Should I do it? I've never been to Lisbon so it would be nice to get a taste. Can I get to and from the airport efficiently? Any other issues to think about?
Thanks.