On 12 January 1807 a ship loaded with gunpowder exploded here in Steenschuur. An entire residential district was destroyed. About 160 people were killed and 2000 injured. Buildings were damaged all over the city. King Louis Bonaparte heard the blast in The Hague and was at the scene within hours. He took charge of the rescue efforts himself and did much to alleviate suffering and help the city recover.

The disaster struck Leiden at a time of decline. The textile industry had gone into a deep recession and there was great poverty. Consequently the scene of the disaster was left unbuilt on.

In 1884 a statue of Burgomaster Van der Werf was erected on the so-called ‘Great Ruin’, with a park surrounding it. Van der Werf was regarded as one of the heroes of the Spanish siege in 1574. He is credited with persuading the people of Leiden not to surrender to the Spanish. In the end the city was liberated. The Relief of Leiden is celebrated each year on 3 October with a street party.

The statue of Van der Werf still plays a role in these festivities as a meeting point.