Baltic approches - two suggestions:
Route TANGO (including the DW route) from bouy Nr. 1 NW of Skagen L/H S through, Kattegat, the Great Belt and Langelandsbælt then forking either E via Fehmahrn Belt to the Baltic (Rostock, Gdansk, Kaliningrad etc.) or W towards the Kieler Canal. This would be the typical route for larger vessels offering lots of anti collison work and a need for a keen eye on your echo sounder. (A radar might be a good idea as well)
For the more experienced master you might add the Western short cut through Little Belt and its opposite Eastern number through the Sound passing the bottleneck at Elsinore and further S across Copenhagen Roads and the very narrow passages E and W of Saltholm and finally exiting at the Falsterbo "roundabout". These are not for the feeble and inexperienced and only take vessels up to 1599 BRT. Especially the Little Belt is a particularly nasty piece of work, its treacherous currents has earned it the nickname "Midshipman killer".
The Sound is a narrow fairway with a heavy traffic load of vessels entering and leaving the Baltic, but also offers a lot of ferries crisscrossing and heaps of fishing ships and pleasure craft always in harms way.
The Baltic approaches in general take all sorts of craft from the 45t fishing vessel to huge RoRos and cruise liners and thus offer the possibility to create a wide range of missions. Depending on what type of vessel the total sailing time from bouy no. 1 to the fork will be 8 - 16 hour real time.
Unfortunately it has been a couple of years since I sailed those waters myself so I cannot give you the corresponding Admiralty chart numbers.