During summer and early fall, the Sumida River was the scene of a custom known as "taking in the cool of the evening." Activity centered at Ryōgoku Bridge, where an endless variety of entertainment was offered on both land and water. The ideal place was not in the crowded stalls of the bridgehead plazas but rather in one of the nearby restaurants or in an individually chartered pleasure boat on the river. Fireworks were an indispensable feature of evenings on the river. By the mid-seventeenth century, they were so popular that the threat of fire led authorities to issue decrees restricting their use to the Sumida River.