Sjávarfoss is a nice waterfall directly in Reykjavík, somewhere hidden under the bridge and at the end of the Elliðaárdalur valley, just few hundred meters/yards before it meets the waters of the Atlantic.
How to find Sjávarfoss (in Reykjavík):
GPS coordinates of the Sjávarfoss waterfall (Reykjavík): 64.123932, -21.841046 Take me there!