You might be tempted to walk on past the staircase that twists its way down the side of this beautiful overlook on the Lisbon coast, and you wouldn’t be alone; most people come here to take in the glorious view of red roofs and cathedrals stretching into the distance towards the Tagus River below and the mountains beyond.

But if you take a second to follow the signs for the public toilet, you'll descend only a short way down the stairs before seeing a tiny tunnel whose curved archway is covered on both sides in a cartoon comic strip depiction of the history of Lisbon by muralist Nuno Saraiva.

If you're lucky, you’ll even encounter a tour guide with a small group of visitors and can eavesdrop on what they're being told about this piece. But if you can’t catch a tour, know that the mural starts with the Phoenicians founding the city they called Ulissipo, continues through the Portuguese Inquisition, depicts the devastating Great Lisbon Earthquake of 1755, and ends nicely with the Carnation Revolution in 1974.

Much has changed in Lisbon since the revolution, a coup on April 25, 1974, that overthrew a dictator to restore democracy in Portugal, and this may be why the artist has chosen to end the illustration with that event. That, and there isn’t much more room left in the tunnel.