Cienfuegos is located on the southern coast of Cuba, about 250 km from Havana. It has a population of 150,000 and called the "Pearl of the South". In 1745 a fortress, "Castillo de Jagua", was erected for protection against pirates. The city was settled in 1819 by french immigrants from Bordeaux & Louisiana. The settlement became a Spanish town in 1829 and a city in 1880. In 2005, UNESCO inscribed the Urban Historic Centre of Cienfuegos on the world heritage list.
I went to Cienfuegos a couple of years ago, the same time I went to Trinidad. Cienfuegos is a beautiful little city. You can walk the entire downtown core in a few hours. There's enough to see within the city and the surrounding area to keep you occupied for a short stay. I would come back and do what I didn't do on my last trip. I regretted not renting a car and travelling around the countryside. If you love nature, there's a lot of it around Cienfuegos. I was fortunate enough to be with a Cuban friend who got us a boat with a captain. We traveled around the bay for the day and ended up having lunch in some remote little village accross the bay. We ate and ate and ate, all seafood, with beer, 6 of us, 40cuc. It was a rediculously cheap for what we got. Otherwise my eating experiences in Cienfuegos were not great. We stayed at the Jagua Hotel http://www.cubahotelreservation.com/hotel.asp?hotel_code=SCTGCJagua which wasn't bad. It had a great view and a pool but only about a 3 star. Good enough for me. It was close enough to everything.
I would probably stay there again. The difference would be that I would do 3 days there and 3 in Trinidad. It's a beautiful part of the country and would recommend seeing it. Don't expect any big city stuff. Relax, take it easy and enjoy the quiet and mother nature.