I've woken up to the strangest sound: silence. It takes a while to sink in. I lie there in bed for a few minutes trying to figure out what's different, what's missing. After a while the realisation dawns that the morning scene is lacking its usual cacophony of car horns, revving motors, yelling taxi wallahs and the occasional explosion of a backfire.
La Paz, a place whose name ironically translates to "peace", is usually anything but peaceful. The Bolivian city's streets are a hellish, 24-hour tangle of traffic, a snarl of buses, trucks, minivans and people.
Up on the high plateau in El Alto it is at its worst. There, single-lane streets are expected to carry the bulk of the city's transport, and you can be stuck at a standstill for hours while traffic lights are ignored and drivers attempt to force their way through vehicular blockades that themselves are trying to force their way in another direction.
You haven't seen a traffic jam until you've been to La Paz.
There are several reasons for this: the swelling population, the lack of infrastructure, the distain for road rules, and the right of the share-taxi minivan drivers and local buses to just stop in the middle of the road to pick up or drop off new passengers, forcing everyone behind them to either stop, or, more likely, tear out onto the other side of the road in an attempt to overtake. That, of course, blocks more traffic coming the other way - so those drivers swerve to the other side of the road in an attempt to find a way through, and you have all the makings of a colossal traffic jam.
It's usually the results of these traffic jams that I can hear when I wake up each morning. Even 10 storeys up, you can't avoid the sounds of La Paz's daily battle for road space. And that's what makes this morning so strange. There's no sound at all. No beeps, no screams, no backfires. Just ... nothing.
I jump out of bed and pull back the curtains, and there, sure enough, is nothing. The streets are completely empty of cars and people. That's when I remember: it's a car-free day. Once a year, the La Paz district enforces a Sunday that is completely free of traffic, where no one is allowed to drive and the tortuously knotted streets are taken over by kids on bikes and families playing football.
It's a token effort to fight the city's noise and air pollution issues, as well as a day to give the streets back to the people.
I hadn't planned my trip around this event, although it's always nice when your travels happen to coincide with something special. It happened last time I was in La Paz, too, when I lucked onto Bolivian Independence Day, a holiday celebrated with endless parades and heroic levels of drunkenness from the local population.
Today, however, I get to experience something different. It's all about family fun on the city's main thoroughfares, and eerie, post-apocalyptic quiet on the back streets.
I start my adventure on those empty lanes, grinning at the tendency of the few pedestrians to stick to the pavements rather than wander straight down the middle of the road. It's habit.
As I get closer to Avenida Perez Velasco, the main pathway between La Paz's old town and midtown, the crowds begin to swell, and everyone is forced to leave the pavements and experience the strange sensation of a fear-free wander down the middle of a La Paz street.
Out on Perez Velasco, there's a party in full swing. Bands play from stages set up on the street. Vendors sell choripan, local sausages that are barbecued and stuffed in bread. There's a whole football pitch that has been set up in one section of the street. Another plays host to kids practising skateboard tricks.
Children ride bikes; a little boy tears down a steep side street on a plastic tricycle, screaming all the way. One family is trying to master hula-hooping. Others are watching the puppet show outside Pollo Rey, the fried-chicken shop.
There's a funny air of joy in the crowd at being allowed the run of the city, at having the freedom of the streets. Teenagers on BMX bikes look like they can't really decide how to use this freedom, so they just mill around in groups. A bunch of dads "accidentally" steal one of their kids' footballs and start a game for themselves.
I'm happy to just wander around and take it all in. Tomorrow the cars, the horns, the yells and the bangs will be back.
For now, however, La Paz really does mean peace.
Have you ever visited a city and lucked into a special celebration? Leave a comment below.