Viðey is great for birdwatching (30 species breed here) and botany (over one-third of all Icelandic plants grow on the island). In late August, some Reykjavikers come to pick wild caraway, which was originally planted here by Skúli Magnússon.
Walking & Cycling
The whole island is criss-crossed with walking paths. Some you can bicycle, others are more precarious. When boats are running from the Old Harbour, you can hire a bike there at Reykjavík Bike Tours and bring it to the island.
From the harbour, trails to the southeast lead past the natural sheep fold Réttin, the tiny grotto Paradíshellir (Paradise Cave) and then to the abandoned fishing village at Sundbakki.
Trails leading to the northwest take you to Vesturey, the northern tip of the island. You'll pass low ponds, monuments to several shipwrecks, and the low cliffs of Eiðisbjarg. Richard Serra’s Áfangar (Standing Stones; 1990) sculptures, made from huge pairs of basalt pillars, dot this northern part of the island.