Base station antennas might look like a pretty simple thing from the outside and at one point that might even have been the case. However, with ever more frequency bands being used by network operators simultaneously at a single site, antenna casings that actually contain more than just a single antenna, or single sets of antennas due to diversity and MIMO, are becoming more common.
The picture on the left for example shows a quad-band base station antenna for simultaneous use of the 800-900 MHZ band (GSM, LTE), 1800 MHz (GSM, LTE), 2100 (UMTS) and 2600 (LTE), UMTS in 2100 and LTE in 2600. And another thing I've seen being presented at MWC right in front rather than in the back is 6-sector antennas with 65 degrees opening angle per sector instead of the 120 degrees three sector antenna configurations used today. Quite an impressive array of feeder cables at the bottom… Very good if that goes hand in hand with base station miniaturization as each sector requires its own "cell" and dedicated resources down in the base station.