Antigua (2 days)
Beautiful 16th-century city built by the Spaniards, with cobblestone
streets, cafes set in lush courtyards, and ruins of churches from an 18th
century earthquake. UNESCO world heritage site. I spent two months
there and could happily spend much more time there.
Tikal (3 days)
Largest Mayan ruins in the world, surrounded by rainforest. Requires
short flight to get there. Gorgeous, relaxing, a must-see.
Lago de Atitlán (2 days)
Breathtakingly beautiful lake, surrounded by volcanoes and interesting Mayan towns.
Great for relaxing or for active sightseeing.
Chichicastenango (1 day)
Colorful Mayan town in the Guatemalan highlands. Come on Sunday or Thursday for its famous market.
Guatemala City (1 day)
Typically tourists stay in Antigua instead of Guatemala City, but it's worth it to hop over to the city if you have time (45-minute drive). This city of 3 million people has some excellent restaurants, good bars and dancing in the Zona Viva, and big movie theaters with most films in English. It's a diverse city. You'll see parts of the city so nice that you won't believe you're in a developing nation (e.g., the Zona Viva); there are parts with beautiful, Spanish-inspired architecture (e.g., Zona 1, the historic city center); and then there are shanty-town neighborhoods that you wouldn't want to go near. Worth seeing: the National Palace and the Museum of Anthropology.
Cobán (2 days)
The town of Cobán is an excellent jumping off point to experience
some of Guatemala's most beautiful nature, including forests, rivers,
Rio Dulce/Livingston (3 days)
Experience a beautiful river on the warm Carribean coast. Meet Guatemalans of the Garifuna culture, completely unlike anyone you'll meet in the rest of the country, and see if your hips can keep up with theirs on the dance floor!