The biggest temple at Baalbek is the Temple of Jupiter. Only six of its columns are still standing, but each one is 20 metres tall - the height of a six-storey building. If you stood at the bottom and looked up, your neck would hurt before you could see the top.
Underneath the temples are foundation stones called the 'Trilithon'. Each of these is around 800 tonnes - heavier than 100 elephants stacked together. Nobody is completely sure how the Romans moved them. There is even a single uncut stone nearby, called the 'Stone of the Pregnant Woman', that weighs more than 1,000 tonnes.
The Temple of Bacchus, right next door, is smaller but in much better condition. Its walls and roof carvings still have detailed patterns of grapes, flowers and leaves cut into the stone. Looking up close at the carvings, you can imagine the stonemasons chipping away for years, one tiny chisel-stroke at a time.
Every summer, Lebanon holds a big music festival inside the ruins - the Baalbek International Festival. Singers, orchestras and dance groups perform with the giant columns lit up behind them. It is one of the most spectacular concert stages in the world.