Housed in an 18th-century building on Barcelona’s Rambla, you can go on guided tours. During your visit, you’ll be able to see the Billeter astronomical clock dating from 1869, which shows the position of the Earth, Sun and Moon, and some of the planets, until the year 2029. You’ll also find the neo-classical assembly room with murals by the painter Fèlix Mestres where Einstein gave his lecture. And finally, don’t miss the clock on the façade. It was designed by Antoni Rigalt and displayed the official time in Barcelona, decreed by the city council, from 1891 until 1941.