If you did not know where it was, you would stroll right past the ruins of the Roman Theater in Cartagena, Spain, one of the largest and best-preserved amphitheaters of the Roman Empire, a theatrical and historical wonder.

The old Roman theater, that sat more than 6,000 people in its heyday, is behind a series of buildings and its entrance is a nondescript door on a large pedestrian plaza, the La plaza del Ayuntamiento (Town Hall Square) in one of the busiest tourist districts of the city. You stand in the middle of the sunny plaza, just a few hundred yards from the Mediterranean Sea, surrounded by cell phones and electronic gadgets of all kind and then step through the nondescript museum entrance into a world that roared with the sounds of cheering theatergoers more than two thousand years ago, all enjoying a play beneath a star filled Spanish sky.

There are about 230 amphitheater ruins in what was the Roman Empire and a number in Greece, too. Greek amphitheaters were built on lawn slopes, but Roman theaters, like this one, constructed in the first century and now part of a museum complex, the Museo Teatromano de Cartagena, were built as free-standing buildings, totally enclosed but without roofs. Plays were first staged in the city of Rome in about 240 BC and quickly became popular in Cartagena when the theater opened.

The amphitheater is dazzling in its architectural majesty. You enter it from a stone corridor that leads out of the museum near the theater’s top seating level and look down at it. The amphitheater is a playhouse with all of the steeply raked rows of seats looking down at a wide stage (covered in wood today). The entrances to the amphitheater were ornate and wide, to permit large crowds to enter and exit easily (try that at a Broadway theater!). You can walk about the amphitheater, too, unlike the sites of many ruins that are mostly roped off to prevent wear and tear. Sightseers can walk to the top of steep stairs that took spectators down to their seats and descend (they are a bit steep). There are five sets of stairs in the lower seating area and seven in the upper seating section. You can walk all the way down to the sizable, 43 meter long stage and then up on to it and stroll around it. In the first century, the stage was decorated with large pillars and several attractive statues (they can be seen in the museum attached to the theater). Just off the stage are the ruins of old rooms used as actors’ dressing rooms and for prop storage. There is a wide plaza to the right for the entrance and exit of actors and props. Men, women and children love to bound about the stage and take photos. There is an actor on stage all day, dressed in a first century Roman soldier’s costume, to answer any questions and pose for photos with you.

The theater, larger than New York City’s famed Radio City Music Hall, was constructed in the early years of the first century and was dedicated to Gauis and Lucius Caesar, the grandsons of Emperor Augustus Caesar. It was built, local historians say, to celebrate the growth of Cartagena. Roman officials liked to build theaters in cities far from Rome to make residents there feel like they were part of the capital since they had a theater, too.

The grand Roman theater did not last long. By the third century A.D. a large market was built over it. Vandals sacked it in 425 and another market was constructed over its grounds in the sixth century. In the 13th century a cathedral was built over much of it and portions of the cathedral remain today. The theater vanished over the years as a city grew above and around it.

The theater was discovered during a general excavation of the area in 1988. Historians said it had remained unknown for so long because many layers of the cities had been built over it.

The museum and theater complex are a little difficult to navigate. You walk in at street level and go into a video room where you watch a documentary on the theater in its heyday. The documentary then shows you the way that the city was built over the theater and how it was identified in 1988, excavated and re-constructed by the Roman Theater Foundation and re-designed by Rafael Moneo. Then you go into a long hall and several rooms off the hall, then take an escalator or elevator to the fourth floor, which is the entrance to the theater itself. The entrance is interesting. The museum architects simply connected the museum to the theater by using a tunnel through the ruins if the old Cathedral. The stones in its walls take you back into time and then, suddenly, there you are at the top of the theater in all its glory.

In the rooms of the museum are interesting pieces of art and sculpture, including many old Roman statutes and some paintings and architectural renderings of what the theater looked like 2,000 years ago. Room one has architectural drawings of the theater. There is a nice model of the theater and the neighborhood around it. In room two you find more artifacts from the theater that help to explain the role the theater played in Cartagenian life and how it was used by the Romans not only to entertain the people but to showcase the power of the Emperor and how much he cared about the colonies, such as Cartagena. Both rooms and a long corridor contain numerous vases that were excavated from the theater site.

If you are in Cartagena, a visit to the theater museum is a nice walk through ancient history. The huge and impressive theater also gives you an idea of the size and grandeur of buildings and cities in that era.

The Roman theater is open Tuesdays through Saturdays, 10 a.m. to 6 p.m. Admission is about $7 (American money). It is located on La plaza del Ayuntamiento