El Salvador has a diverse spread of attractions considering its small size. San Salvador and Santa Ana have the top landmarks, with the latter boasting the highly rated El Teatro. There are also quality beaches like Costa del Sol and amazing national parks—be sure to check out Los Volcanes National Park on a day tour from the capital.

National Theater of Santa Ana

El Teatro Nacional is the main landmark of Santa Ana, residing in the old part of the city along Avenida Independencia. The three-tiered theater harks back to the early 1900's and features a grand façade with balcony, lobby, and beautifully crafted stage and house. Performances are put on year-round.
Address: Avenida Independencia Norte, Santa Ana
Phone: +503-2447-6268
Website: n/a

National Anthropology Museum

Arguably El Salvador’s top museum, the Museo Nacional de Antropología is an unassuming, modern building that is loaded with incredible exhibits spread across two floors. The history of the country is well covered, especially that of the mysterious Mayan empire who left behind many traces of their reign. Arts, music and religion are all incorporated, and there’s a pleasant garden to meander through. It's worth noting that the descriptions are only in Spanish (so bring a translator) and the museum is closed on Mondays.
Address: Av La Revolución Zona Rosa, San Salvador
Phone: +503-2243-3927
Website: n/a

Joya de Cerén

El Salvador’s most impressive Mayan ruins—the "Pompeii of the Americas"—are not far from the main route between the capital and Santa Ana. They are well preserved, after being discovered in the ash from the nearby Loma Caldera eruption for 1,400 years. The ancient farming community features living quarters, kitchens, workshops, and even a sauna.
Address: La Libertad, Canton Joya de Cerén
Phone: n/a
Website: http://whc.unesco.org/en/list/675/

Tazumal

A must for those into Mayan history, Tazumal is a stunning climbable pyramid near the town of Santa Ana. "The place where victims were burned" is one of the top archeological sites of its kind in the entire region, covering almost four-square miles. The ruins lie in the town of Chalchuapa, which is west of Santa Ana en-route to the sublime El Imposible National Park via RN-13.
Address: Chalchuapa, West of Santa Ana
Phone: n/a
Website: n/a

Playa El Esteron

Playa El Esteron at El Cuco on the south coast is one of the nicest beaches in El Salvador. It is quiet though you can enjoy water sports here. There are several hotels in the area with shuttles to other nearby beaches, including Playa Las Flores (the best for surfing) and Intipuca.
Address: El Cuco, South Coast
Phone: n/a
Website: n/a

Costa del Sol

The middle of the El Salvador Pacific coast is home to the aptly named "Sun Coast." Like its Spanish counterpart, it has an expansive stretch of golden sand popular with high-end visitors who stay in the villas and tasteful hotels that back the beaches. Costa del Sol is not far to the south of San Salvador and is within striking distance of the stunning San Juan del Gozo peninsula. Beaches here include Los Blancos and San Marcelino.
Address: Central Coast
Phone: n/a
Website: n/a

Suchitoto

This pretty lakeside town in the north is a popular weekend retreat for San Savadorans and is a must for those into the country’s Spanish colonial past. There are many examples of these, though none as well located as Suchitoto. The streets are made of cobblestone and in the center of town is an impressive church and square, while a craft market is open most days. Boat tours circle the lake, or you could dine at La Posada Suchitlán's waterfront. 
Address: Central-North El Salvador
Phone: n/a
Website: n/a

Volcanoes National Park

Also known as Cerre Verde National Park, Parque Nacional Los Volcanes is home to three major volcanoes and is not far west of San Salvador. Hiking is the main pastime and either Santa Ana or Izalco can be done in one day. There’s also a forested walk for those less outdoorsy. The visitor center has maps of the routes and it is possible to camp overnight in the park.
Address: Parque Nacional Los Volcanes, Western El Salvador
Phone: n/a
Website: n/a

El Imposible National Park

El Imposible is situated in the far west of El Salvador and is more in-tune with nature than nearby Volcanoes National Park. It is also less crowded, which means people come here to spot the rare wildlife and take in miles of well-marked trails. The park rises over 4,600 feet and encompasses rainforests and waterways with beautiful viewpoints.
Address: Ahuachapan, Western El Salvador
Phone: n/a
Website: n/a