Turkey has approved development of a new canal beside the Bosporus
The Bosporus is Turkey's, but due to the 1936 Montreux Convention it can't allow non-Black Sea State navy ships to pass through, and it can't charge for the passage of civilian vessels during peacetime. The new Istanbul Canal would not have such restrictions.
It is expected to be around 45km long, 21m deep, and 360-275m wide (top and bottom) and cost $15b. It will sit around 30km west of the Bosporus Straight, and will be spanned by 6 bridges, all high enough to clear the largest ships (which will cost another $1.4b).
Currently, ships have to wait around 14 hours to enter the Black Sea due to congestion of the Bosporus. Estimates have it that revenue from the canal could amount to $8b per year eventually, if vessels decide to pay, which it is uncertain they will. Turkey will also be able to send dangerous cargo on a route further away from the city center.
Istanbul citizens polled in 2020 opposed the project (80% opposed) due to environmental and other effects they will be faced with. It's also opposed by Russia which sees the potential ability of US and NATO warships to enter the Black Sea as a national security threat. 104 former Turkish naval officers also publicly opposed the project (the next day 10 were arrested).