A few blocks away to the east is the city's oldest square, Plaza Constitucion, overlooked by ancient buildings, like the Cathedral, and the Cabildo, the old Spanish Colonial City Hall. Today the Cabildo is a historical museum with archives, maps, photos, artwork and other items relating to the city's tumultuous history. As the city's former political center, this was where the country's new constitution was signed after independence from Spain. There was even a prison on the premises long ago. If you're visiting the city on weekends, check out the vendors selling crafts in the square and on the streets leading from it, especially the pedestrianized Calle Sarandi. You'll find handmade jewelry, souvenirs, small paintings, and the high-quality leather accessories Uruguay is known for. Take note, as you walk along, of the ornate turn-of-the-last-century commercial buildings being restored along the route.

A Spanish citadel once stood here in colonial days, and the only remnant is its portal, on the west side of the Plaza, which serves as the gateway to Ciudad Vieja. The wide plaza is surrounded by historical and modern buildings, a major crossing point between old and new sections of the city. Its main feature is the oversized and gallant statue of General José Gervasio Artigas, the hero of Uruguay's independence movement.

Take the stairs below the statue for his funky '70s era mausoleum, which is lit like the basements in teenage slasher movies. Oversized concrete letters jut from the walls telling his life story, casting strange shadows everywhere. And, as if in a time warp, an ancient ornamental urn sits under glass in the center, surrounded by austere and silent soldiers in colonial-era costumes. You might just be lucky enough to catch the changing of the guards down here too, which is the only time they seem relaxed—perhaps relieved to get out of the darkness.

Your four-hour visit has ended where history began. Head up the stairs out of the creepy basement mausoleum and back above ground into the shining South American sun to say goodbye to Montevideo.