The largest outdoor sight in downtown Beirut hearkening back to the days when the city was a centre of Roman law, the baths here underwent a major renovation in the 1990s. The ingenious ancient heating system, called a hypocaust, is gloriously apparent here: stacked terracotta discs conducted hot air to the marble floors above, on which bathers of all social classes would let the stress melt away. The site also includes a medicinal plant garden.