I’ve hiked most of the trails in Wicklow Mountains National Park. Glendalough is a fantastic starting point for a number of walking routes in the valley at all levels of difficulty.
Glendalough loop walk in Wicklow Mountains.
Drive to Glendalough Visitor Car park or Glendalough Upper Lake Car Park. One of the most spectacular trails is a loop around Glendalough Upper lake through Miners Village. Hiking up is rewarded by stunning views of the Glenealo Valley. I highly recommend hiking the full loop which is around 10 km (takes about 2 – 4 hours) depending on weather coditions and your fitness level. The weather can be very ungreateful in the valley, it is often rainy with a limited visibility. This walk is suitable for dogs but on other routs in Wicklow Mountains you will not be able to take your friend due to signs ‘No dogs allowed’.
From the Glendalough Upper Lake Car Park there are number of marked trails, which start from half an hour walks up to the 10 km full loop. Remember that weather conditions may be slightly different (or even very different) from the starting point. I experienced heavy rain and wind while hiking the full loop. Keep in mind to wear warm clothes, rain and windproof coat and good hiking shoes.
If you are considering hiking the highest peak in Wicklow Mountains – Lugnaquilla, here is some good advice (I’ve done it in tough winter conditions and mild spring): https://freestyletraveling.com/lugnaquilla-highest-mountain-in-wicklow/