As Chicago's populace swelled, the sewer system became increasingly strained and by the 1960s, the sewers overflowed on over 100 days annually. This led to the introduction of the Deep Tunnel system.

The deep-level tunnels do however have one powerful sell that should help it pull in UK visitors year-round: It’s somewhere to go when it’s raining.

HS2's first deep tunnel, which took 15 months to dig and is under ancient Warwickshire woodland, has reached a construction milestone. Civil engineering works, including concrete finishing works ...